Support `working-directory` in action configuration

[lbhm]

I am using uv in a project with multiple components written in different languages. Let's assume that the Python component is in ./python/. When using the uv action, I would like to be able to switch to the Python component directory first instead of always installing the virtual environment at the top level.

Many other actions support the working-directory key. Would this also be possible for setup-uv?

[eifinger]

Related: #251