[ci skip] Document PublicExceptions middleware
[ci skip] document ActionDispatch::FileHandler
[ci skip] Document ActionDispatch::Static
Uppercase HTML in docs.

[skip ci]
Small grammar fix in pluck description
`overriden` => `overridden`
[ci skip] Update links in getting_started guide.
[ci skip] Update plugin doc with the latest rails
[ci skip] config.active_record.errors_in_transactional_callbacks -> config.active_record.raise_in_transactional_callbacks
4.2 Release Notes pass [skip ci]
Merge pull request #16552 from untidy-hair/update_plugin_guide

[ci skip] Update plugin doc with the latest rails
use same idiom to define class method as in every other adapter.
"warning: assigned but unused variable"
Merge pull request #16554 from y-yagi/patch-2

[ci skip] config.active_record.errors_in_transactional_callbacks -> config.active_record.raise_in_transactional_callbacks
Gem `queue_classic` does not support JRuby
Skip adapter queue_classic for JRuby
Merge pull request #16556 from jonatack/patch-9

4.2 Release Notes pass [ci skip]
Merge pull request #16559 from splattael/jruby-queue_classic

Do not depend on queue_classic on JRuby
Merge pull request #16487 from jayshepherd/patch-1

Small grammar fix in pluck description
minor copy editing [ci skip]