Config file placed at the project level at `.config/irb/irbrc` is not parsed.

The documentation states that:

The path to the configuration file is the first found among:
File +.config/irb/irbrc+ in the current directory, if it exists.

https://github.com/ruby/irb/blob/master/lib/irb.rb#L148

but there seems to be no code which would do this. Creating such file does nothing in reality as well: I have a project under ~/projects/notes and if I create a config file at ~/projects/notes/.config/irb/irbrc and put something like puts "test" there, nothing is printed when I run irb being at the project root.

https://github.com/ruby/irb/blob/35b87cf8933f67cf6e9e0edd1ca7d6395595a758/lib/irb/init.rb#L451

I really see beneficial to put a config file just under .config/irb/irbrc of my project instead of polluting project root, so I would like to double-check that it is a bug, rather than misleading documentation.

Start by comparing the documented search order in lib/irb.rb around line 148 with the configuration lookup in lib/irb/init.rb around line 451. Reproduce the issue from a project root containing .config/irb/irbrc and verify that the file is loaded when running irb; done means the documented project-level path is parsed as described.