Update Docs On All Relevant Merges

Recently https://github.com/karma-runner/karma/pull/3761 got merged, updating some docs. However the corresponding Release workflow did not trigger updating the public website. We should ensure that the Karma website docs get updated as soon as a modification to their markdown source is merged in this repository, even if the merge did not trigger a release.

@devoto13 WDYT?

Inspect the Release workflow and the markdown sources that feed the public Karma website. Reproduce the merge scenario described in the issue, then verify that changing and merging documentation updates the website without requiring a release.

Written by the indexing model from the issue text.