[DOCS] Document _mvt API

docs/build.gradle

@@ -68,6 +68,9 @@ testClusters.matching { it.name == "integTest"}.configureEach {
       setting 'es.shutdown_feature_flag_enabled', 'true'
     }
     systemProperty 'es.geoip_v2_feature_flag_enabled', 'true'
+    if (BuildParams.isSnapshotBuild() == false) {
+      systemProperty 'es.vector_tile_feature_flag_registered', 'true'
+    }
     keystorePassword 'keystore-password'
   }
 

docs/reference/search.asciidoc

@@ -39,6 +39,12 @@ exception of the <<search-explain,explain API>>.
 * <<multi-search-template>>
 * <<render-search-template-api>>
 
+ifdef::permanently-unreleased-branch[]
+[discrete]
+[[geo-search-apis]]
+=== Geospatial search
+* <<search-vector-tile-api>>
+endif::[]
 
 include::search/search.asciidoc[]
 
@@ -75,3 +81,7 @@ include::search/profile.asciidoc[]
 include::search/field-caps.asciidoc[]
 
 include::search/rank-eval.asciidoc[]
+
+ifdef::permanently-unreleased-branch[]
+include::search/search-vector-tile-api.asciidoc[]
+endif::[]