[TEST!] Publish Logstash plugins from main to be consumed by logstash-docs-md

[colleenmcginnis]

Publishes Logstash plugin pages (like this page in the Logstash Reference guide) from main so they can be consumed by logstash-docs-md to be published on elastic.co/docs.

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[colleenmcginnis]

This should no longer be necessary. We're using a different approach.