Add github action

.github/workflows/release.yml

@@ -0,0 +1,36 @@
+name: Release Apk
+
+on:
+  push:
+    branches:
+    - main
+    
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+    
+    - uses: actions/checkout@v1
+    - uses: actions/setup-java@v1
+      with:
+        java-version: '12.x'
+        
+    - uses: subosito/flutter-action@v1
+      with:
+        channel: 'stable'
+        flutter-version: '2.5.3'
+    
+    - run: flutter pub get
+    
+    - run: wget "${{secrets.KEY_FILE_URL}}" > android/app/fjy.androidstudio.key
+    
+    - run: wget "${{secrets.KEY_PROP_URL}}" > android/key.properties
+    
+    - run: ./make.dart build android
+
+    - run: echo "APP_VER=$(git log --oneline | wc -l | xargs)" >> $GITHUB_ENV
+    
+    - uses: actions/upload-artifact@v1
+      with:
+        name: Release Apk
+        path: release/Toolbox_${{ env.APP_VER }}_Arm64.apk