[DOCS] Document the `string_distance` parameter for term suggestor

docs/reference/search/suggesters/term-suggest.asciidoc

@@ -9,70 +9,70 @@ suggest text is analyzed before terms are suggested. The suggested terms
 are provided per analyzed suggest text token. The `term` suggester
 doesn't take the query into account that is part of request.
 
-==== Common suggest options: 
+==== Common suggest options:
 
 [horizontal]
-`text`:: 
+`text`::
     The suggest text. The suggest text is a required option that
     needs to be set globally or per suggestion.
 
-`field`:: 
+`field`::
     The field to fetch the candidate suggestions from. This is
     an required option that either needs to be set globally or per
-    suggestion. 
+    suggestion.
 
-`analyzer`:: 
+`analyzer`::
     The analyzer to analyse the suggest text with. Defaults
-    to the search analyzer of the suggest field. 
+    to the search analyzer of the suggest field.
 
-`size`:: 
+`size`::
     The maximum corrections to be returned per suggest text
-    token. 
+    token.
 
-`sort`:: 
+`sort`::
     Defines how suggestions should be sorted per suggest text
     term. Two possible values:
 +
-    ** `score`:     Sort by score first, then document frequency and 
-                    then the term itself. 
+    ** `score`:     Sort by score first, then document frequency and
+                    then the term itself.
     ** `frequency`: Sort by document frequency first, then similarity
-                    score and then the term itself. 
+                    score and then the term itself.
 +
-`suggest_mode`:: 
+`suggest_mode`::
     The suggest mode controls what suggestions are
     included or controls for what suggest text terms, suggestions should be
-    suggested. Three possible values can be specified: 
-+    
+    suggested. Three possible values can be specified:
++
      ** `missing`:  Only provide suggestions for suggest text terms that are
-                    not in the index. This is the default. 
+                    not in the index. This is the default.
      ** `popular`:  Only suggest suggestions that occur in more docs then
-                    the original suggest text term. 
+                    the original suggest text term.
      ** `always`:   Suggest any matching suggestions based on terms in the
                     suggest text.
 
-==== Other term suggest options: 
+==== Other term suggest options:
 
 [horizontal]
-`lowercase_terms`:: 
-    Lower cases the suggest text terms after text analysis. 
+`lowercase_terms`::
+    Lower cases the suggest text terms after text analysis.
 
-`max_edits`:: 
+`max_edits`::
     The maximum edit distance candidate suggestions can
     have in order to be considered as a suggestion. Can only be a value
     between 1 and 2. Any other value result in an bad request error being
-    thrown. Defaults to 2. 
+    thrown. Defaults to 2.
 
-`prefix_length`:: 
+`prefix_length`::
     The number of minimal prefix characters that must
     match in order be a candidate suggestions. Defaults to 1. Increasing
     this number improves spellcheck performance. Usually misspellings don't
-    occur in the beginning of terms. (Old name "prefix_len" is deprecated) 
+    occur in the beginning of terms. (Old name "prefix_len" is deprecated)
 
-`min_word_length`:: 
+`min_word_length`::
     The minimum length a suggest text term must have in
     order to be included. Defaults to 4. (Old name "min_word_len" is deprecated)
 
-`shard_size`:: 
+`shard_size`::
     Sets the maximum number of suggestions to be retrieved
     from each individual shard. During the reduce phase only the top N
     suggestions are returned based on the `size` option. Defaults to the
@@ -81,24 +81,24 @@ doesn't take the query into account that is part of request.
     corrections at the cost of performance. Due to the fact that terms are
     partitioned amongst shards, the shard level document frequencies of
     spelling corrections may not be precise. Increasing this will make these
-    document frequencies more precise. 
+    document frequencies more precise.
 
-`max_inspections`:: 
+`max_inspections`::
     A factor that is used to multiply with the
     `shards_size` in order to inspect more candidate spell corrections on
     the shard level. Can improve accuracy at the cost of performance.
-    Defaults to 5. 
+    Defaults to 5.
 
-`min_doc_freq`:: 
+`min_doc_freq`::
     The minimal threshold in number of documents a
     suggestion should appear in. This can be specified as an absolute number
     or as a relative percentage of number of documents. This can improve
     quality by only suggesting high frequency terms. Defaults to 0f and is
     not enabled. If a value higher than 1 is specified then the number
     cannot be fractional. The shard level document frequencies are used for
-    this option. 
+    this option.
 
-`max_term_freq`:: 
+`max_term_freq`::
     The maximum threshold in number of documents a
     suggest text token can exist in order to be included. Can be a relative
     percentage number (e.g 0.4) or an absolute number to represent document
@@ -108,3 +108,15 @@ doesn't take the query into account that is part of request.
     usually spelled correctly on top of this also improves the spellcheck
     performance. The shard level document frequencies are used for this
     option.
+
+`string_distance`::
+    Which string distance implementation to use for comparing how similar
+    suggested terms are. Five possible values can be specfied:
+    `internal` - The default based on damerau_levenshtein but highly optimized
+    for comparing string distancee for terms inside the index.
+    `damerau_levenshtein` - String distance algorithm based on
+    Damerau-Levenshtein algorithm.
+    `levenstein` - String distance algorithm based on Levenstein edit distance
+    algorithm.
+    `jarowinkler` - String distance algorithm based on Jaro-Winkler algorithm.
+    `ngram` - String distance algorithm based on character n-grams.