ci: Add rust-test workflow

This runs tests and formats code.

.github/workflows/rust-test.yml

@@ -0,0 +1,25 @@
+name: Rust Test
+
+# Run this workflow whenever a PR is created or pushed to.
+on:
+  pull_request:
+    types: [opened, synchronize]
+
+jobs:
+  rust-test:
+
+    runs-on: ubuntu-latest
+
+    steps:
+    - name: Checkout code
+      uses: actions/checkout@v3
+
+    - name: Run tests
+      run: |
+        cd scubainit
+        cargo test
+
+    - name: Code format
+      run: |
+        cd scubainit
+        cargo fmt --check