Adding filetype icons for more formats

I've been working with .ts and .tsx files as part of a next.js development. Both of these filetypes have syntax support, but MacVim doesn't come bundled with icons for these filetypes. I was able to generate some on my own and, with a few hacks on the command line, get my own macvim installation to show them in finder, and get finder to use macvim to open them.

I thought about trying to add these icons here to the repo, but wanted to check with the dev team first on a few things:

1. Is there an established template for these icon files? I just photoshopped these together quickly (matching the font/colors/etc. of existing filetype icons), but if there's a source file I could simply edit and export to the same format you already use, I'd rather do that, and generate assets that match what you already are using
2. The CONTRIBUTING.md file here looks like it comes from vim directly, but regardless, there's a note in there about "not causing trouble with trademarks" -- I think these files are above board (i.e., they don't use any microsoft design language, just plain TS and TSX text), but want to make sure this is OK

I also know it takes more than just creating some images to get this to work -- namely some changes in the main Info.plist for the app to handle the associations properly -- but will hold on any of that until I get a nod here one way or another.

Finally, .ts is also apparently an extension tied to a standard MPEG video format, and if you have an app like VLC installed, it wants to claim the association instead. Just a possible collision that could result if we wanted the app to try to associate itself with that filetype.

まず既存のファイルタイプアイコンのアセットと CONTRIBUTING.md を確認して、確立されているテンプレートと商標に関するガイダンスを把握し、その後、Info.plist でのアプリのファイル関連付けの処理を調べます。.ts と .tsx に対応するアイコンが追加され、関連付けの動作（.ts と MPEG の衝突の可能性を含む）が解決されるか、明示的に文書化されていれば完了です。