👷 Define testing workflow

Defines a Github Action to run the Jest test suite

.github/workflows/main.yml

@@ -0,0 +1,11 @@
+name: Run Tests
+on: push
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v4
+    - name: Install modules
+      run: yarn
+    - name: Run tests
+      run: yarn test