UI: Add data-pagefind-meta attribute on repeatable UX elements

[regisphilibert]

Currently it's impossible to CSS target a result tag based on the meta it holds as its produced html is simply:

<li class="pagefind-ui__result-tag svelte-xxxx">Genre: Litterature</li>

By adding a simple attribute to it, it would allow users to style them differently based on the meta.

The following would enable CSS targeting for repeatable elements such as result tags.

<li class="pagefind-ui__result-tag svelte-xxxx" data-pagefind-meta="Genre">Genre: Litterature</li>

This could also be applied to

• . pagefind-ui__filter-block
• Other repeatable elements I'm not aware of :)

[bglw]

Great idea! Will do.