Better block level whitespace removal. Removes any whitespace immediately preceding block level opening tags or following block level closing tags.
Fix issue with function assignment.
Add <li> as block tag. MDN doesn't list this, but it defaults to display:block.
Make removeBlockWhitespace remove any between a block tag and another tag. It seems like removal should only occur outside of block tags (as before). But this matches the behavior expected by Quill's unit tests.