Added Github Actions for CI

.github/workflows/flutter_build_test.yml

@@ -0,0 +1,51 @@
+name: Flutter CI for TripItOn
+
+# This workflow is triggered on pushes to the repository.
+
+on:
+    push:
+        branches:
+            - master
+    pull_request:
+        branches:
+            - master
+
+# on: push    # Default will running for every branch.
+
+jobs:
+    build:
+        # This job will run on ubuntu virtual machine
+        runs-on: ubuntu-latest
+        steps:
+            # Setup Java environment in order to build the Android app.
+            - uses: actions/checkout@v1
+            - uses: actions/setup-java@v1
+              with:
+                  java-version: "12.x"
+
+            # Setup the flutter environment.
+            - uses: subosito/flutter-action@v1
+              with:
+                  channel: "beta" # 'dev', 'alpha', default to: 'stable'
+                  # flutter-version: '1.12.x' # you can also specify exact version of flutter
+
+            # Get flutter dependencies.
+            - run: flutter pub get
+
+            # Check for any formatting issues in the code.
+            - run: flutter format --set-exit-if-changed .
+
+            # Statically analyze the Dart code for any errors.
+            - run: flutter analyze .
+
+            # Run widget tests for our flutter project.
+            - run: flutter test
+
+            # Build apk.
+            - run: flutter build apk
+
+            # Upload generated apk to the artifacts.
+            - uses: actions/upload-artifact@v1
+              with:
+                  name: release-apk
+                  path: build/app/outputs/apk/release/app-release.apk