Added "Create folder" keyboard shortcut

[takshittt]

Fixes #3383, #3376

Changes:

• Added a keyboard shortcut for creating a new folder: Ctrl/Cmd + Alt/Option + Shift + N.
• This follows common conventions in development environments and avoids conflicts with existing shortcuts used by the editor or browsers.

I have verified that this pull request:

• has no linting errors (npm run lint)
• has no test errors (npm run test)
• is from a uniquely-named feature branch and is up to date with the develop branch.
• is descriptively named and links to an issue number, i.e. Fixes #3383, #3376

[yugalkaushik]

@takshittt The Ctrl/Cmd + Alt/Option + Shift + N shortcut feels a bit tricky to use, such long key combinations don't really function as shortcuts anymore. I'd suggest switching to something shorter, like Ctrl/Cmd + Shift + N, after verifying no conflicts.