The syntax highlighter only supports [source,js].
Also adds a check to the rest test generator that runs during
the build that'll fail the build if it sees `[source,json]`.
* Centralised plugin docs in docs/plugins/
* Moved integrations into same docs
* Moved community clients into the clients section of the docs
* Removed docs/community
Closes#11734Closes#11724Closes#11636Closes#11635Closes#11632Closes#11630Closes#12046Closes#12438Closes#12579