Please add explaination to README how to run ZeroNet with tor

You should add a section: "Tor connectivity", and explain there that by default ZeroNet connects through the clearnet, and requires either UPnP feature on the router, or manually opened port #. In case of ```--tor=always```, on the other hand, open port isn't needed, but torrc should have ..... and explain what is actually required from Tor.

This pertains to basic connectivity, and should be in README, IMO.

Read the README and locate the appropriate place for a new “Tor connectivity” section. Document the default clearnet behavior, UPnP or manually opened ports, the --tor=always case, and the required torrc configuration; done means these connectivity requirements are explained clearly in the README.

索引モデルが issue の本文から書いたものです。