Repo maintenence changes

[rsb-23]

Originally posted by @rsb-23 in #569

Some changes can be done to improve the maintenance of the project.

• Set dependabot frequency = monthly. So, we have to review only 1 PR for deps upgrades.
• Build time can be reduced to < 5 min.
• ...

...will keep adding, if there is any other possibility.

[svenjacobs]

How can the build time be reduced?

[rsb-23]

Maybe caching and running parallel builds.
This will also reduce workflow runtime (takes about 8m now).