ES|QL Add full-text search to the functions docs page (#116024)

Now that the match and qstr functions are Tech Previewing, we should add them to the top-level functions doc page.

Co-authored-by: Craig Taverner <craig@amanzi.com>

docs/reference/esql/esql-functions-operators.asciidoc

@@ -48,6 +48,12 @@ include::functions/ip-functions.asciidoc[tag=ip_list]
 include::functions/math-functions.asciidoc[tag=math_list]
 ====
 
+.*Search functions*
+[%collapsible]
+====
+include::functions/search-functions.asciidoc[tag=search_list]
+====
+
 .*Spatial functions*
 [%collapsible]
 ====
@@ -89,6 +95,7 @@ include::functions/conditional-functions-and-expressions.asciidoc[]
 include::functions/date-time-functions.asciidoc[]
 include::functions/ip-functions.asciidoc[]
 include::functions/math-functions.asciidoc[]
+include::functions/search-functions.asciidoc[]
 include::functions/spatial-functions.asciidoc[]
 include::functions/string-functions.asciidoc[]
 include::functions/type-conversion-functions.asciidoc[]

docs/reference/esql/esql-limitations.asciidoc

@@ -102,11 +102,19 @@ is currently experimental.
 
 [discrete]
 [[esql-limitations-full-text-search]]
-=== Full-text search is not supported
+=== Full-text search
+
+experimental:[] {esql}'s support for <<esql-search-functions,full-text search>>
+is currently in Technical Preview. One limitation of full-text search is that
+it is necessary to use the search function, like <<esql-match>>, in a <<esql-where>> command
+directly after the <<esql-from>> source command, or close enough to it.
+Otherwise, the query will fail with a validation error.
+Another limitation is that any <<esql-where>> command containing a full-text search function
+cannot also use disjunctions (`OR`).
 
 Because of <<esql-limitations-text-fields,the way {esql} treats `text` values>>,
-full-text search is not yet supported. Queries on `text` fields are like queries
-on `keyword` fields: they are case-sensitive and need to match the full string.
+queries on `text` fields are like queries on `keyword` fields: they are
+case-sensitive and need to match the full string.
 
 For example, after indexing a field of type `text` with the value `Elasticsearch
 query language`, the following `WHERE` clause does not match because the `LIKE`

docs/reference/esql/functions/search-functions.asciidoc

@@ -0,0 +1,16 @@
+[[esql-search-functions]]
+==== {esql} Full-text search functions
+
+++++
+<titleabbrev>Full-text Search functions</titleabbrev>
+++++
+
+{esql} supports these full-text search functions:
+
+// tag::search_list[]
+* experimental:[] <<esql-match>>
+* experimental:[] <<esql-qstr>>
+// end::search_list[]
+
+include::layout/match.asciidoc[]
+include::layout/qstr.asciidoc[]