feat(bindings): support Cmd/Ctrl-Shift-Z hot key for history redo

[giamir]

Closes #187

Describe your changes

This PR adds support for Shift-Mod-Z as hot key for history redo. It removes a utility that was used to create double bindings for both uppercase and lowercase hot keys containing letters (Mod-z and Mod-Z). Instead it introduces a plugin that normalizes letter case for keydown events based on the status of the Shift key:

• when Shift is pressed letter case is always uppercase
• when Shift is NOT pressed letter case is always lowercase

The plugin also helps to normalize the different Keyboard Events behavior across operative systems when caps lock is enabled. For historical context please refer to this old issue: https://github.com/StackExchange/Stacks-Editor/issues/90

PR Checklist

• [x] All new/changed functionality includes unit and (optionally) e2e tests as appropriate
• [x] All new/changed functions have /** ... */ docs
• [x] I've added the bug/enhancement and other labels as appropriate

Environment(s) tested

• Device: PC - OS: Windows 10 - Browser: Chrome
• Device: MacBook Pro - OS: MacOS Monterey - Browser: Chrome, Safari, Firefox, Edge

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