Show demographics relative to number of inhabitants

See https://2025.stateofcss.com/en-US/demographics/

USA is on top. That's not really interesting, since the USA is a very big country.

We know big countries are big.

What would be much more interesting, is a list of countries sorted relative to the number of inhabitants,
so you get a better view on how involved people are in certain countries.

Start at the linked demographics page and trace how its country ranking and participation values are assembled. Determine the population data source and normalization needed for an inhabitants-relative comparison. Done means the countries are ordered by participation relative to population, with the result visible on the demographics page.

Written by the indexing model from the issue text.