Add unit testing

.github/workflows/unit.yml

@@ -0,0 +1,16 @@
+name: Unit Tests
+
+on: [push, pull_request]
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions-rs/toolchain@v1
+        with:
+          profile: minimal
+          toolchain: stable
+          override: true
+      - run: cargo test
+        working-directory: crates/hirola-core