Add tip about using RDoc's --pipe command to quickly test the output of
a piece of documentation.

This can be useful for trying out combinations of markup and code, as
discussed in rails/rails@225bcad
Revert "speed up the collection proxy reader method, but slow down the constructor"

This reverts commit f9e4c3c7c0c4152b62fe9202a9d12262884bb118.

[fixes #14116]
Add regression test for collection proxy reader

[related #14116]
[skip ci] Fix the javascript path in guide for asset modules
Merge branch 'master' of github.com:rails/docrails
Merge pull request #14124 from arthurnn/fix_14116

Fix collection proxy exists? regression
Merge pull request #14086 from jingweno/master

Fix the javascript path in guide for asset modules [skip ci]