Android: Make touch joystick re centering configurable

Source/Android/app/src/main/res/values/strings.xml

@@ -246,6 +246,7 @@
     <string name="emulation_toggle_controls">Toggle Controls</string>
     <string name="emulation_toggle_all">Toggle All</string>
     <string name="emulation_control_scale">Adjust Scale</string>
+    <string name="emulation_control_joystick_rel_center">Relative Stick Center</string>
     <string name="emulation_choose_controller">Choose Controller</string>
     <string name="emulation_controller_changed">You may have to reload the game after changing extensions.</string>