Add application/typescript
Unfortunately, unless the uncommon .cts file extension is used (indicating a CommonJS module written in TypeScript), TypeScript files do not have any clear identifying marks. TypeScript files with a .ts or .mts extension can only be distinguished from MPEG transport streams and Qt Linguist catalogs by exclusion: If no magic matches, then the file is probably TypeScript.
According to the TypeScript specification: "Every JavaScript program is also a TypeScript program."
https://github.com/github-linguist/linguist/blob/7ca3799b8b5f1acde1dd7a8dfb7ae849d3dfb4cd/lib/linguist/languages.yml#L7165 https://javascript.xgqfrms.xyz/pdfs/TypeScript%20Language%20Specification.pdf