Update XML to v0.0.7

[sweetppro]

remove hard coded path extensions in favor of first_line_pattern regex

[notpeter]

first_line_pattern = '^<.*xml'

Is there a reason you're not just using <\? *xml - Are there other possibilities for valid XML headers besides which you are trying to match besides these:

<?xml 
<? xml
<?        xml

[sweetppro]

Xliff files for example can use something like:
<xliff xmlns="urn:oasis:names:tc:xliff:document:1.2" version="1.2">

[notpeter]

FYI I added a little bit of official docs for this too.
So if your regex isn't working for folks they can just add their own extensions.
https://zed.dev/docs/languages/xml

[sweetppro]

@notpeter when will the update be live in the gallery?