Add IME support (#991)

data/core/rootview.lua

@@ -334,6 +334,9 @@ function RootView:on_text_input(...)
   core.active_view:on_text_input(...)
 end
 
+function RootView:on_ime_text_editing(...)
+  core.active_view:on_ime_text_editing(...)
+end
 
 function RootView:on_focus_lost(...)
   -- We force a redraw so documents can redraw without the cursor.