Add unit tests for parsing connection frames

There's a bit of complexity in byte-level parsing of serial/BLE frames, so I thought it would be helpful to add unit tests to ensure correct behavior.

.github/workflows/test.yml

@@ -0,0 +1,14 @@
+name: Run tests
+
+on: push
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-node@v4
+        with:
+          node-version: 20
+      - run: npm ci
+      - run: npm test