CI: add "ci:ignore-count" and "ci:skip-build"
Allow skipping the "too many packages changed" check by specifying "ci:ignore-count" in the commit message.
Allow skipping the package build step by specifying "ci:skip-build" in the commit message. In contrary to the usual "skip ci" method, this will still run all the other CI checks.
@PureTryOut: when this MR is merged, you can specify
[ci:skip-build] in the last commit of plasma/kde/... updates, and it will still run all the other checks.