fix github actions

[wickedOne]

currently there are several issues (possibly related) with this repo's github actions:

duplicate runs:

actions are triggered by both the push and pull_request events.
if someone pushes an additional commit / rebased branch to an existing pull request, both events are fired causing all actions to be fired twice. apparently these events have a different ${github.ref} so using this in the concurrency setting won't solve the issue.

possible solution might be either to fix it through the concurrency setting adding a conditional or referencing an environment variable which is constant between both events or do something fancy in the workflow event definition

merge dependabot upgrades:

these continue to fail with the following message

An error occurred while merging the Pull Request. This is usually caused by the base branch being out of sync with the target branch. In this case, the base branch must be rebased. Some tools, such as Dependabot, do that automatically.

possibly the merge-me action gets confused by the duplicate runs, so hopefully fixing the first point of this issue will solve this one. if not some further investigation is needed