Improve highlither for document edits

The syntax highlighter keep a cache of the documents like tokenization.

In order to minimize the amount of tokenize re-computations we insert some
emtty lines or remove some lines in the highlither lines corresponding to
the lines added or removed to the document.

data/core/doc/init.lua

@@ -348,7 +348,7 @@ function Doc:raw_insert(line, col, text, undo_stack, time)
   push_undo(undo_stack, time, "remove", line, col, line2, col2)
 
   -- update highlighter and assure selection is in bounds
-  self.highlighter:invalidate(line)
+  self.highlighter:insert_notify(line, #lines - 1)
   self:sanitize_selection()
 end
 
@@ -375,7 +375,7 @@ function Doc:raw_remove(line1, col1, line2, col2, undo_stack, time)
   end
 
   -- update highlighter and assure selection is in bounds
-  self.highlighter:invalidate(line1)
+  self.highlighter:remove_notify(line1, line2 - line1)
   self:sanitize_selection()
 end