docs(readme): update min. requirements + cleanup (#10750)

* docs(readme): update min. requirements + cleanup

Adding note about extra memory requirement due to
https://github.com/ipfs/kubo/commit/ba22102a640b3f41804319981d83908c96a96275



* docs(config): memory cost of buffered provider

Co-authored-by: Daniel Norman <1992255+2color@users.noreply.github.com>