Add task to get hash

[roaldarbol]

To make it easier to find the SHA256, I've made a task that fetches the SHA256. It is run this way:

pixi run get-hash <url-to-package>

So example:

pixi run get-hash https://github.com/roaldarbol/academicv/archive/refs/tags/v1.1.1.tar.gz

Solves #35.

[roaldarbol]

Seems the pixi version in the setup-pixi workflows need to be bumped to make use of args in tasks.