Add views chart to README

[m-aciek]

Since June we track the visitors and pageviews of the docs. It'd be nice to have a statistics of viewing figures of Polish part of docs. I think of a second chart below the progress one (or above?).

https://analytics.python.org/docs.python.org?f=contains,page,/pl/

[StanFromIreland]

Plausible allows for embedding of the dashboard, I wonder if it allows for filters. If it does it could do what we want?