Add plausible analytics to header

[kandarpksk]

I would like to track clicks to specific links in the header "CryoET Data Portal" and "Browse Data" (except from home page itself) to understand usage relative to breadcrumbs.

Metadata: kind of page the link is clicked from (single-run, single-dataset, single-deposition)

This would help us compare usage of the header vs breadcrumbs (and whether breadcrumbs need to be more visible). For reference, this is the issue about tracking of breadcrumb clicks: #1238 (comment)