Editor bugs

[yuhan0]

Issue:

Attempting to enter a literal string with newlines causes the cell to break into two invalid cells. Pressing backspace to fix the issue crashes the webpage and the entire document is corrupted upon refresh:

A similar thing happens when the user tries to delete from the start of a cell adjacent to another cell above, the contents of the second cell disappear after the crash and can't be retrieved:

Environment:

• Browser: Firefox
• Platform (Mac/Windows/Linux): Mac

URL to a gist replicating the issue (if possible/relevant)

[yuhan0]

Another bug: typing Space after a single : or :: inserts the keyword :lark.tree.parse/error directly before the cursor.

Also, commas are currently highlighted red like syntax errors (they aren't), and the editor moves the cursor backward when trying to type spaces after a comma