Docs: Update plugins.asciidoc

add search by sql

Closes #7525

docs/reference/modules/plugins.asciidoc

@@ -274,6 +274,7 @@ You can disable that check using `plugins.check_lucene: false`.
 * https://github.com/elasticsearch/elasticsearch-lang-groovy[Groovy lang Plugin]
 * https://github.com/elasticsearch/elasticsearch-lang-javascript[JavaScript language Plugin]
 * https://github.com/elasticsearch/elasticsearch-lang-python[Python language Plugin]
+* https://github.com/NLPchina/elasticsearch-sql/[SQL language Plugin] (by nlpcn)
 
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