Implement GitHub action for auto building stuff

[xADDBx]

I just found out that it's not possible to just grant access to repository that you don't own. Meaning
To make this work, you'd need to:

1. Create an Api Key with read:packages permissions here
2. Create a Repository secret which contains the API Key here
3. In each of the 3 .yml workflow files, replace
   GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
   with
   GITHUB_TOKEN: ${{ secrets.MY_REPO_SECRET_NAME }}

If I did everything right, then even though I changed some stuff in the csproj, the project should still work completely the same for you.
You might want to squash the commits if you merge.