Enable release keysigning for APK

AppImageBuilder.yml

@@ -2,10 +2,7 @@
 version: 1
 script:
   - rm -rf AppDir || true
-  - rm -rf build || true
   - rm -rf appimage-build
-  - flutter pub get
-  - flutter build linux
   - cp -r build/linux/x64/release/bundle AppDir
   - mkdir -p AppDir/usr/share/icons/hicolor/64x64/apps
   - cp Icons/PNG/nbteditor.png AppDir/usr/share/icons/hicolor/64x64/apps/
@@ -34,13 +31,13 @@ AppDir:
       - libwayland-cursor0
   files:
     include:
-    - /lib64/ld-linux-x86-64.so.2
+      - /lib64/ld-linux-x86-64.so.2
     exclude:
-    - usr/share/man
-    - usr/share/doc/*/README.*
-    - usr/share/doc/*/changelog.*
-    - usr/share/doc/*/NEWS.*
-    - usr/share/doc/*/TODO.*
+      - usr/share/man
+      - usr/share/doc/*/README.*
+      - usr/share/doc/*/changelog.*
+      - usr/share/doc/*/NEWS.*
+      - usr/share/doc/*/TODO.*
 AppImage:
   arch: x86_64
   update-information: guess