Added support for prerelease and nightly repos

[sauk2]

Closes #17

Summary

This PR adds support to ubuntu-prerelease and ubuntu-nightly Gazebo repositories.

Two additional tests have been added to the workflow to test the installation of harmonic on jammy and noble using the unstable repos.

[j-rivero]

Thanks for the PR!

Both prelease and nighly can be installed together, both requires to have gazebo-stable but all three can be working perfectly. Let's change the code so we can use that option.

In the PR we also need documenttion in the README about how to use these options.

[sauk2]

Thanks for the PR!

Both prelease and nighly can be installed together, both requires to have gazebo-stable but all three can be working perfectly. Let's change the code so we can use that option.

In the PR we also need documenttion in the README about how to use these options.

Updated the function to allow both the nightly and prerelease together. All checks pass. Will be adding tests and updating README!

[sauk2]

@j-rivero Added unit tests and updated README with instructions. All checks pass!

[j-rivero]

Minimal suggestion to document the problem on Noble. Good to go. Great work !