Docs: Update plugins.asciidoc

Closes #6683

docs/reference/modules/plugins.asciidoc

@@ -229,6 +229,7 @@ You can disable that check using `plugins.check_lucene: false`.
 * https://github.com/kzwang/elasticsearch-river-dynamodb[DynamoDB River Plugin] (by Kevin Wang)
 * https://github.com/salyh/elasticsearch-river-imap[IMAP/POP3 Email River Plugin] (by Hendrik Saly)
 * https://github.com/codelibs/elasticsearch-river-web[Web River Plugin] (by CodeLibs Project)
+* https://github.com/eea/eea.elasticsearch.river.rdf[EEA ElasticSearch RDF River Plugin] (by the European Environmental Agency)
 
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