For now the project is badly covered by the tests. It can be greatly improved.

Given this XML file:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE article [
  <!ENTITY mdash "&#x2014;">
]>
<root>
  &mdash
</root>

There is an error for &mdash because it misses ; we should provide a code action to fix that to insert at the end of &mdash the missing ;