Support for hangul alt chars

[Tyriar]

Part of #196203

TODO

• Move into a new file (altChars.ts?) as this concept could be used elsewhere
• Fixing lint by explicitly allowing unicode chars in this file as they make it much more readable/maintainable
• Reduce string/array creation
• Reduce repetition, for example when looking at char indexes in the character data
• Consider optimizing/compressing the hangul character data
• Add unit tests

[Tyriar]

@TylerLeonhardt what do you think about this new "alternate characters" concept? This could be adopted by other languages as needed. Here's what I plan on doing on the PR still but don't have time this iteration:

(moved to top)

[TylerLeonhardt]

I like the approach and think this is a good list of tasks. I wonder if there are other places where we can use this (settings editor, keybindings editor, etc)

[Tyriar]

Where ever this shared filtering code is used they'll get it for free, but I'm also planning on making it its own independent module if something else wants to integrate 👍

[Tyriar]

@TylerLeonhardt this is pretty solid now, it doesn't work in go to file through which is one of the big use cases. I'm not sure if I can easily add it to go to file?

[Tyriar]

Note that this does not work in contiguous searches, so it must match from the start of the word. It's a hard optimization problem to get it to work for contiguous string checking too, at least without changing how that works to get off indexOf