FR: Update README and documentation to indicate current installation instructions and pip support

[jcurtis-cc]

Hi there,

A gentle push to update the docs to indicate the status of a working install, and which platforms are actually supported currently.

[inikishev]

what is the current installation instruction?

[dreddi]

Hey guys, see my instructions for a static Linux build here (on Ubuntu 22.04): https://github.com/MTG/essentia/discussions/1295