Added unit tests, vitest, coverage.

.github/workflows/ci.yml

@@ -78,6 +78,20 @@ jobs:
           name: maputnik-windows
           path: ./desktop/bin/windows/
 
+  unit-tests:
+    name: "Unit tests"
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v5
+      - run: npm ci
+      - run: npm run test-unit-ci
+      - name: Upload coverage reports to Codecov
+        uses: codecov/codecov-action@v5
+        with:
+          files: ${{ github.workspace }}/coverage/coverage-final.json
+          verbose: true
+
   e2e-tests:
     name: "E2E tests using chrome"