Add back to editor button

mods/common/languages/en.ftl

@@ -228,6 +228,12 @@ dialog-play-map-warning =
     errors preventing it from being loaded.
     .cancel = Okay
 
+dialog-exit-to-map-editor =
+    .title = Leave Mission
+    .prompt = Leave this game and return to the editor?
+    .confirm = Back To Editor
+    .cancel = Stay
+
 ## IngamePowerBarLogic
 ## IngamePowerCounterLogic
 label-power-usage = Power Usage: { $usage }/{ $capacity }