Don't show snippets for user tags with spaces in name

If you have a user tag with spaces in it's name, like:

src/main/resources/templates/tags/my tag.html

Then a snippet for my tag appears. When you apply the snippet, qute-ls reports that the generated code is an error.

It's not clear from the Qute documentation what should be done in this case, however accepting the snippet and trying to render the template results in an error. Also, trying variations on the name like my-tag, mytag, myTag still results in the template failing to render. I think we should avoid suggesting completions for any user tags with spaces in their name.

Start by tracing qute-ls completion handling for user tags, using the example template path src/main/resources/templates/tags/my tag.html as the reproduction case. Verify that tags whose names contain spaces are excluded from suggested snippets and that the resulting completion behavior no longer produces invalid generated code.