Add a workflow to run unit tests

.github/workflows/build.yml

@@ -73,6 +73,31 @@ jobs:
         with:
           arguments: ${{ inputs.flavour }}
 
+  unit-tests:
+    runs-on: ubuntu-latest
+    # to prevent running unit tests twice; on the internal and external workflow.
+    if: inputs.internal == false
+    needs: [ build ]
+
+    steps:
+      - name: Unit tests (Debug)
+        uses: gradle/gradle-build-action@v3
+        with:
+          gradle-version: ${{ inputs.gradle_version }}
+        run: ./gradlew :app:testNoapiX64GeckoGenericDebugUnitTest
+             ./gradlew :app:testNoapiArm64GeckoGenericDebugUnitTest
+
+      - name: Unit tests (Release)
+        uses: gradle/gradle-build-action@v3
+        with:
+          gradle-version: ${{ inputs.gradle_version }}
+        run: ./gradlew :app:testNoapiX64GeckoGenericReleaseUnitTest
+             ./gradlew :app:testNoapiArm64GeckoGenericReleaseUnitTest
+
+  deploy:
+    runs-on: ubuntu-latest
+
+    steps:
       - name: Upload APK (without WebXR support) to Artifacts
         uses: actions/upload-artifact@v4
         with: