Support for auto-updating the uv version

[burgholzer]

Hey 👋🏼

Thanks for your work on this project! Integrating it into some of our repositories over at https://github.com/cda-tum was pretty smooth sailing and works nicely. Consider this issue more a request for comment or a suggestion and not as an issue per se.

Right now, the action will (rightfully, imo) emit a warning when not specifying an explicit version of uv to use.
However, not specifying a version generally lowers the maintenance overhead as one keeps automatically getting new versions.
If I would specify a version explicitly (maybe even using SemVer to permit patch version updates), I would have to manually check for new versions continuously and update them in all projects that use this action.
Given that the version is specified as an option to the action, this is cannot be simply updated by dependabot and I am not really aware of any other solutions for automating that particular setting. (that might just be my ignorance, though 😅)

Over at nox (and probably many others, such as cibulidwheel) this is solved by versioning the action with the same version as the tool the action provides. For convenience, some of those repositories provide additional (moving) tags for their actions that would, e.g., allow for action versions such as @2.5, which would correspond to ~2.5.0 in SemVer or @2, which would correspond to ~2.0.
This kind of versioning policy of the action allows for using dependabot to get automatic updates through CI, while still giving the user the option to decide which granularity of SemVer they want to go for.

Would you consider something like that? Feel free to close this issue if you feel that this is totally out of scope for this action here 😌
(Technically, one could directly bring this up to the folks at @astral-sh and ask if they would be willing to set something like that up.)