DOM document should store Invalid end tag </

[angelozerr]

While working on #881 I notice that it was very hard to support usecase with invalid end tag </ (it's hard for instance to detect it to eat it for instance with code action).

The main problem is that DOM document doesn't stores this invalid end tag.

We can see this problem for instance if you have this XML:

<a>
  </
</a>

The outline doesn't show the </ (although it shows start tag like < and if you format this XML you loose the </ content.