Add workflow for building debug apk

.github/workflows/apk_debug.yml

@@ -0,0 +1,35 @@
+name: Build Debug APK
+
+on:
+  pull_request:
+  push:
+    branches: master
+
+jobs:
+  apk:
+    name: Build Debug APK
+    runs-on: ubuntu-latest
+    environment:
+      name: apk_build
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v3
+        with:
+          ref: refs/pull/${{github.event.pull_request.number}}/merge
+
+      - uses: ./.github/actions/checkout_submodules
+
+      - name: Setup Java
+        uses: actions/setup-java@v2
+        with:
+          distribution: 'zulu'
+          java-version: '17'
+
+      - name: Build debug APK
+        run: ./gradlew assembleDebug
+
+      - name: Upload APK
+        uses: actions/upload-artifact@v1
+        with:
+          name: app
+          path: app/build/outputs/apk/debug/app-debug.apk

.github/workflows/apk_main.yml

@@ -1,4 +1,4 @@
-name: Build APK for master
+name: Build Release APK for main branch
 
 on:
   push:

.github/workflows/apk_pr.yml

@@ -1,4 +1,4 @@
-name: Build APK for PR
+name: Build Release APK for pull requests
 
 on:
   pull_request_target:

README.md

@@ -20,7 +20,7 @@ You can also update the submodule with this command.
 ### Build
 If you want to build an APK, run the following command:
 ```
-./gradlew :app:buildDebug
+./gradlew :app:assembleDebug
 ```
 The resulting APK will be stored in `app/build/outputs/apk/debug/app-debug.apk`.