There's a closed pull request on the void-packages repository

isl: update to 0.22.1
https://github.com/void-linux/void-packages/pull/24424

Description:
I edited the template, the corresponding soname and revbumped all involved.
It builds clean on my machine.
I'm not sure how to include vlicense() for MIT.
This is my first pull request, I hope I didn't mess anything up.