Deduplicate Pagefind filters

[bglw]

If you tag one page with duplicate filters (i.e. have data-pagefind-filter="site:Blog" multiple times on one page) then filter counts in that category will be double counted, as the page will be recorded in that filter index multiple times.

At indexing time, the parser should de-duplicate filters to prevent this.

[distinctperspective]

Any update??