feat: enable dev menu on Android (#602)

Overridded method that is called on the key event on which the developer menu on Android should be opened. Change added only for debug mode. Should resolve #276.
Clicking cmd+m on macOS in debug mode should open the developer menu on Android, but Action Bar wants to handle that key event in order to trigger showOverflowMenu on the Toolbar. We then override this method and call React's showDevOptionsDialog in it.

android/src/main/java/com/swmansion/rnscreens/ScreenStackHeaderConfig.java

@@ -18,6 +18,7 @@
 import androidx.appcompat.widget.Toolbar;
 import androidx.fragment.app.Fragment;
 
+import com.facebook.react.ReactApplication;
 import com.facebook.react.bridge.JSApplicationIllegalArgumentException;
 import com.facebook.react.views.text.ReactFontManager;
 
@@ -45,6 +46,19 @@ public class ScreenStackHeaderConfig extends ViewGroup {
   private int mDefaultStartInset;
   private int mDefaultStartInsetWithNavigation;
 
+  private static class DebugMenuToolbar extends Toolbar {
+
+    public DebugMenuToolbar(Context context) {
+      super(context);
+    }
+
+    @Override
+    public boolean showOverflowMenu() {
+      ((ReactApplication) getContext().getApplicationContext()).getReactNativeHost().getReactInstanceManager().showDevOptionsDialog();
+      return true;
+    }
+  }
+
   private OnClickListener mBackClickListener = new OnClickListener() {
     @Override
     public void onClick(View view) {
@@ -67,7 +81,7 @@ public ScreenStackHeaderConfig(Context context) {
     super(context);
     setVisibility(View.GONE);
 
-    mToolbar = new Toolbar(context);
+    mToolbar = BuildConfig.DEBUG ? new DebugMenuToolbar(context) : new Toolbar(context);
     mDefaultStartInset = mToolbar.getContentInsetStart();
     mDefaultStartInsetWithNavigation = mToolbar.getContentInsetStartWithNavigation();