Add copy of OFL to our embedded fonts folder

[mitchellh]

From #2671

We should audit and ensure we're in compliance with our embedded font licenses. I checked when I added them and I'm pretty sure they're all OFL. But the OFL requires a copy of the license:

Original or Modified Versions of the Font Software may be bundled,
redistributed and/or sold with any software, provided that each copy
contains the above copyright notice and this license. These can be
included either as stand-alone text files, human-readable headers or
in the appropriate machine-readable metadata fields within text or
binary files as long as those fields can be easily viewed by the user.

Fonts: https://github.com/ghostty-org/ghostty/tree/main/src/font/res

The only font that ends up in the final release is JB Mono. The rest are only used for unit tests (but still require license compliance).

[ngynkvn]

I went ahead and checked all of the font files using https://fontdrop.info/?darkmode=true.

They are all under OFL-1.1 or MIT (Only CozzetteVector was MIT licensed)

Is this as simple as including a copy of OFL.txt inside of the directory? If so, #2688 adds a copy of the text

[mitchellh]

I believe so. I think it may be worth adding a README.md in there also stating that every font in this directory is licensed under OFL, just to be explicit.

[mitchellh]

Done with #2688. @ngynkvn can you also confirm you give me permission to relicense your commits as MIT? (not the fonts since I can't do that, but your modifications to our repo)