Add examples/p2p-multiwriter

[jaredatron]

I've created this additional example in hopes to illustrate (and personally learn) how to achieve a basic peer-to-peer multi-writer setup using Hypercore 10.

See README.md for more.

I am hoping to get feedback on how I can better use Corestore, Hyperswarm and Autobase API's as intended. For example I am manually merging streams right now in a way that I think Autobase was specifically designed for. If someone can guide me, I would be happy to put more time into improving this example.

Thank you so much!

[mafintosh]

Thanks! We'll try to land this asap :)

[mafintosh]

cc @andrewosh

[jaredatron]

Thanks! I would love to contribute to examples and documentation however I can as I learn. I'm also happy to move this to the https://github.com/hypercore-protocol/p2p-multiwriter-with-autobase repo if that is a better home for it.