perf(seo): koniec ze zmiana adresu CSS przy kazdym commicie - #254

Search Console crawl stats, read today for the first time: 25% of Googlebot's
requests on this site are CSS, and only 10% of all requests are discovery. Two
of fifty-three pages carry 78% of impressions and thirty-six pages are not
indexed at all, while the crawler spends a quarter of its budget re-reading
normalize.css.

The cause is one Liquid expression. The stylesheet href appended
site.github.build_revision - the commit SHA - so every commit produced a
different URL for a file that had not changed. Thirty commits in two days is
thirty stylesheets as far as a crawler is concerned.

It was buying nothing, and that was checked against the live response rather
than reasoned about: GitHub Pages serves this with Cache-Control max-age=600
and an ETag. Without any buster the worst case is a ten-minute-old stylesheet,
and the ETag usually prevents even that. The buster was solving a problem the
CDN had already solved, and charging the crawl budget for it.

Worth noting what this does not fix. Position is the real problem - the two
pages carrying the impressions sit at 36 and 54, which is page four and page
six - and no amount of crawl budget moves that. This frees the budget to find
the pages that are already written; ranking them is the HP and IIS work.