Feat: add support for upcasing, downcasing, and capitalizing word

[3N4N]

PR Summary

Closes #2912

GNU Readline provides functionalities which let the user change the case of the word in front of the cursor. They can change the word to upper case or lower case, or they can capitalize it. The keybindings by default provided are as follows.

bind '"\ec": capitalize-word'    # default is alt-c
bind '"\eu": upcase-word'     # default is alt-u
bind '"\el": downcase-word'  # default is alt-l

This PR brings that functionality to PSReadLine.

The newly added bindable functions are in the "Basic editing functions" section:

• CapitalizeWord, bound to Alt+c and Escape,c in Emacs mode
• DowncaseWord, bound to Alt+l and Escape,l in Emacs mode
• UpcaseWord, bound to Alt+u and Escape,u in Emacs mode

PR Checklist

• PR has a meaningful title
  • Use the present tense and imperative mood when describing your changes
• Summarized changes
• Make sure you've added one or more new tests
• Make sure you've tested these changes in terminals that PowerShell is commonly used in
  • conhost.exe (with MockPSConsole)
  • Windows Terminal (with MockPSConsole)
  • Visual Studio Code Integrated Terminal
• User-facing changes
  • Not Applicable
  • OR
  • Documentation needed at PowerShell-Docs
    • Doc Issue filed: Three new functions added to PSReadLine bindable functions MicrosoftDocs/PowerShell-Docs#9033

Microsoft Reviewers: Open in CodeFlow

[ghost]

All CLA requirements met.

[3N4N]

@lzybkr Hi, again. Some of the requirements have not been fulfilled (writing tests, adding docs). I need help with that. And being unfamiliar with the codebase, what I've come up with must be riddled with bugs. Need review on the actual code, too. You understand.

[lzybkr]

@3N4N - thanks for the contribution - @daxian-dbw is the PSReadLine maintainer now.

[3N4N]

Any chance of it getting reviewed? An update would be nice.

[daxian-dbw]

@3N4N thanks for submitting the PR, we will review it the next Monday. Every Monday is our community day, where we focus on PRs and issues.

[3N4N]

Thanks.

[3N4N]

All suggestions except the tests have been committed. I'll get to the tests soon.

[3N4N]

@daxian-dbw All suggestions committed. Tests for all three functions added.

[daxian-dbw]

LGTM
I pushed a commit to fix up a few minor issues, and also added descriptions for the new public functions.

[3N4N]

Thanks @daxian-dbw for the merge.

[ghost]

🎉 v2.3.0-beta0 has been released which incorporates this pull request. 🎉