adding script to generate signed release bundle

tools/generate-release.sh

@@ -0,0 +1,10 @@
+#! /bin/bash
+
+./gradlew clean bundleRelease -Punsigned --no-daemon --no-configuration-cache --no-build-cache
+RELEASE_AAB=app/build/outputs/bundle/release/app-release.aab
+
+jarsigner -verbose -sigalg SHA256withRSA -digestalg SHA-256 \
+  -keystore .secrets/upload-key.jks \
+  -storepass $1 \
+  $RELEASE_AAB \
+  key0