[Devel] Git workflow updates

Hello everyone,

As described in [0], we’ve been using specially formatted commit messages for a while now to automate closing and referring issues. Please try to follow the updated guidelines when submitting your contributions.

To summarise the guidelines, Apertis issues referred in the commit messages are transferred into the package’s changelog when it’s updated using `gbp dch` tool. When the package is uploaded, apertis-qa-bot will automatically update the status of the issues in Phabricator as the package is built and installed into the images.

[0]: https://wiki.apertis.org/Guidelines/Contribution_process