Switch to GameActivity and gradle build

Fixes: https://github.com/damus-io/notedeck/issues/189
Fixes: https://github.com/damus-io/notedeck/issues/190
Signed-off-by: William Casarin <jb55@jb55.com>

crates/notedeck_chrome/android/build.gradle

@@ -0,0 +1,9 @@
+// Top-level build file where you can add configuration options common to all sub-projects/modules.
+plugins {
+    id 'com.android.application' version '8.4.1' apply false
+    id 'com.android.library' version '8.4.1' apply false
+}
+
+task clean(type: Delete) {
+    delete rootProject.buildDir
+}