build: add debug workflow and improve release workflow

.github/workflows/debug-build.yml

@@ -0,0 +1,37 @@
+name: "Debug Build"
+
+on:
+  push:
+    branches:
+      - "master"
+    tags-ignore:
+      - "*"
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v1
+      - name: Set up JDK 12
+        uses: actions/setup-java@v1
+        with:
+          java-version: '12.x'
+      - uses: subosito/flutter-action@v1
+        with:
+          channel: 'stable'
+      - name: Set up Flutter
+        run: flutter pub get
+      - name: Generate files with Builder
+        run: flutter packages pub run build_runner build --delete-conflicting-outputs
+      - name: Build with Flutter
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        run: flutter build apk --debug
+      - name: Publish debug APK
+        uses: "marvinpinto/action-automatic-releases@latest"
+        with:
+          repo_token: "${{ secrets.GITHUB_TOKEN }}"
+          automatic_release_tag: "latest"
+          prerelease: true
+          title: "Development Build"
+          files: build/app/outputs/flutter-apk/app-debug.apk