Create template and github action for building pull-requests

[MDK5]

Currently testers need to either download the repository and build the plugin themselves or the creator needs to manually attatch an up-to-date build artifact to the pr. An automated GitHub action would make both creating a pr and keeping track of the latest build artifact a lot easier.

Additionally, a pr-template similar to Artemis's template explaining e.g. how to install the artifact would further speed up the process.