Reasons:
1. `pnpm` is now an industry standard, being faster and less buggy than `yarn`.
2. Faster build time as builds are concurrent: 63 seconds down to 35 seconds!!
3. Resolves #9412
Co-authored-by: ThatOneCalculator <kainoa@t1c.dev>
Reviewed-on: https://codeberg.org/calckey/calckey/pulls/9461
