fix(jqLite): use XHTML-compliant HTML as input for jqLite

[mgol]

What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)

Bug fix.

What is the current behavior? (You can also link to an open issue here)

#6917

What is the new behavior (if this is a feature change)?

Closing tags are added to HTML passed to jqLite which should make it XHTML-compliant.

Does this PR introduce a breaking change?

No.

Please check if the PR fulfills these requirements

• The commit message follows our guidelines
• Fix/Feature: Docs have been added/updated (N/A)
• Fix/Feature: Tests have been added; existing tests pass (we don't test on XHTML so it can't be tested)

Other information:

Fixes #6917

[Narretz]

Should we add a note to the docs that input to jqlite must be XHTML compliant? This does affect user-code, too, right?

[mgol]

Should we add a note to the docs that input to jqlite must be XHTML compliant? This does affect user-code, too, right?

Yes, but only if they care about XHTML which the vast majority of users doesn't do (and doesn't need to).

What note would you have in mind?

[Narretz]

Hm I guess if somebody cares about XHTML compliance then they should be aware of this. No need to add a note.