🔨 Include both <sth> and <element name="sth"> in hover

[babakks]

Fixes microsoft/vscode#160987

[babakks]

@aeschli I used | (pipe) as the joiner for possible element signatures, like:

<something>|<element name="something">

Of course, this change of behavior of the MarkedStringPrinter class resulted in other tests failing. I wasn't sure that you're okay with the changes that I made in this PR. So, I left other test cases as they were, until hearing your opinion on this.

[aeschli]

Thanks @babakks. I'm sorry, but I don't think that's the right fix.
[name='something'] should give the hover <element name="something">
<something> is wrong and is the bug.

Note that <element name="something"> is not something you can write in HTML. The element is just used as a placeholder for any element name.

The bug is that the Element class uses the name property to store the element name, but name is a valid attribute, so that conflicts. Instead of name, the element name should be stored in a separate property, or something like <>` should be used which is not a valid attribute name.