Replicate Vim backspace and CTRL-C behaviour (#129)

data/core/keymap.lua

@@ -154,10 +154,13 @@ function keymap.on_key_pressed(k)
         return true
       end
     elseif mode == 'insert' then
-      if stroke == 'escape' then
+      if stroke == 'escape' or stroke == 'ctrl+c' then
         core.set_editing_mode(core.active_view, 'command')
         return true
       end
+      if stroke == 'backspace' then
+        command.perform('doc:backspace')
+      end
       return false
     end
     local commands = keymap.map[stroke]