Try GitHub actions for CI

.github/workflows/ci.yml

@@ -0,0 +1,10 @@
+steps:
+- uses: actions/checkout@v3
+- name: Install poetry
+  run: pipx install poetry
+- uses: actions/setup-python@v4
+  with:
+    python-version: '3.10'
+    cache: 'poetry'
+- run: poetry install
+- run: poetry run inv tests