Adds nightly action to update VERSION file for pip packaging

[kellyguo11]

Description

The Isaac Lab pip package requires an update for the VERSION file to trigger a new package build for pypi. This PR adds an automated github action job that runs at 00:00 UTC time every day. The job checks whether any new changes were made to the main branch apps/ or source/ folders on that day and creates a commit to bump the VERSION content if new changes exist.

[Toni-SM]

VERSION increase for Python package should only be applied when there are changes in the source and apps folders.
Changes only in scripts or docs, for example should not update version for Python packages as the package content will remain unchanged.

Also, what happens if we change the version manually? The pipeline will also increase it, and the final version will be the (original) version + 2

[kellyguo11]

VERSION increase for Python package should only be applied when there are changes in the source and apps folders. Changes only in scripts or docs, for example should not update version for Python packages as the package content will remain unchanged.

Also, what happens if we change the version manually? The pipeline will also increase it, and the final version will be the (original) version + 2

That's a good point, let me see if we can check for changes in just those 2 folders. I think we should avoid updating VERSION manually if we go with an automated job and only do a manual update for major releases. The automated job should make it easier to maintain rather than having us manually update the VERSION each time.