Update analysis.asciidoc (#37404)

STConvert plugin is made by Medcl to convert between Simplified Chinese and Traditional Chinese. It's widely used by the Search Community for Chinese

docs/plugins/analysis.asciidoc

@@ -58,6 +58,7 @@ A number of analysis plugins have been contributed by our community:
 * https://github.com/ofir123/elasticsearch-network-analysis[Network Addresses Analysis Plugin] (by Ofir123)
 * https://github.com/medcl/elasticsearch-analysis-string2int[String2Integer Analysis Plugin] (by Medcl)
 * https://github.com/ZarHenry96/elasticsearch-dandelion-plugin[Dandelion Analysis Plugin] (by ZarHenry96)
+* https://github.com/medcl/elasticsearch-analysis-stconvert[STConvert Analysis Plugin] (by Medcl)
 
 include::analysis-icu.asciidoc[]