Enhance codimd role

This MR describes the enhancements I made, when adjusting the role for my own use.

I split up relevant changes/additions in single commits, so it is easier to overview the changes and decide on them. This is just a proposal and I wanted to present them all in one context. Some changes may not be needed in your use case and I can always adjust the MR and remove the specific functionality, that you do not want. But all in all this should work out of the box and in the default configuration should work with your setup. (Only the install location change might be breaking, depending on your variable definitions. But this can also be discussed)

Each commit has a description, that describes the change, so instead of listing all changes here, please view the respective commit messages :)

Thank you for the awesome role and for open sourcing your whole setup.