Update search-template.asciidoc

Clarified using the conditional clause template example as a string

docs/reference/search/search-template.asciidoc

@@ -163,6 +163,7 @@ We could write the query as:
 [source,js]
 ------------------------------------------
 {
+  "query": {
     "filtered": {
       "query": {
         "match": {
@@ -185,6 +186,7 @@ We could write the query as:
         {{/line_no}} <2>
       }
     }
+  }
 }
 ------------------------------------------
 <1> Fill in the value of param `text`
@@ -196,11 +198,22 @@ We could write the query as:
 <6> Include the `lte` clause only if `line_no.end` is specified
 <7> Fill in the value of param `line_no.end`
 
+[NOTE]
+==================================
 As written above, this template is not valid JSON because it includes the
-_section_ markers like `{{#line_no}}`.  For this reason, the template
-can only be written as a string.
+_section_ markers like `{{#line_no}}`.  For this reason, the template should
+either be stored in a file (see <<pre-registered-templates>>) or, when used 
+via the REST API, should be written as a string:
+
+[source,json]
+--------------------
+"template": "{\"query\":{\"filtered\":{\"query\":{\"match\":{\"line\":\"{{text}}\"}},\"filter\":{{{#line_no}}\"range\":{\"line_no\":{{{#start}}\"gte\":\"{{start}}\"{{#end}},{{/end}}{{/start}}{{#end}}\"lte\":\"{{end}}\"{{/end}}}}{{/line_no}}}}}}"
+--------------------
+
+==================================
 
 [float]
+[[pre-registered-templates]]
 ===== Pre-registered template
 
 You can register search templates by storing it in the `config/scripts` directory, in a file using the `.mustache` extension.