Adds fragments() and fragmentsIf() method

[arkoe]

Adds fragments() and fragmentsIf() function.
With htmx (and probably similar libraries) you can swap out of bounds, allowing you to update multiple sections of a page, requiring multiple fragments. The current way to do this is by concatenating two (or more) fragments:

return view('welcome')->fragment('fragment1') . view('welcome')->fragment('fragment2');

With fragments() this is simplified to:

return view('welcome')->fragments(['fragment1', 'fragment2']);

or

return view('welcome')->fragments('fragment1', 'fragment2');

---

Also a fragmentsIf() to conditionally return these fragments have been added in this PR. This is basically an expansion on PR #45656, allowing you to conditionally return multiple fragments:

return view('welcome')->fragmentsIf(request()->hasHeader('HX-Request'), ['fragment1', 'fragment2']);

or

return view('welcome')->fragmentsIf(request()->hasHeader('HX-Request'), 'fragment1', 'fragment2');