GitHub workflows for build and testing

[yonas]

The tests/test.py exits with a Connection refused error in GitHub's CI, but works fine for me locally.

Here's the minuimum that works without error:

name: Testing

on:
  push:
    branches: [ "main" ]
  pull_request:
    branches: [ "main" ]

jobs:
  build:
    runs-on: ubuntu-latest

    steps:
    - uses: actions/checkout@v4

    - name: make
      run: make

[cozis]

Much appreciated! Can you change the PR target to the dev branch? I try to avoid pushing directly to main. We should probably include dev in the workflow too

[yonas]

I've added dev to the target branches. You'll want to include main so that people can easily see the results.