Create branch if not existent, else update

[katexochen]

I always want to copy my file to a specific branch.
If I use the destination_branch option, the action throws an error when the given branch does not exist.
Else, if I use the destination_branch_create, the action creates the branch if it doesn't exist, but fails if it exists instead of updating it.
There are of course ways to check if the branch exists and chose the right option based on this, but it would be nicer if the default would just be to create a branch if it doesn't exist and to update if it exists (like the copycat action does).

[dmnemec]

Seems like a good idea.

[hugoheml]

I think we can use the destination_branch_create parameter but I'm not sure, we need to test.