CI : Pin github actions to full commit SHA

[Aniketsy]

https://github.com/numpy/numtype/blob/main/.github/workflows/ci.yml#L23

i think we should pin full commit SHA instead of tags.

Please let me know your thoughts on this. Thanks!

[jorenham]

Yea good idea. We should probably set up Zizmor as well.

[Aniketsy]

Yea good idea. We should probably set up Zizmor as well.

sure 👍 , should i open a seprate issue for the Zizmor setup.

[jorenham]

That works; but it's also fine to re-use this one