Paid site hosting

## Motivation

The site currently remains online so long as at least 1 peer is serving it.

This is good, but what if all the visitors suddenly stop hosting the site? It will go down.

## Solution

Free hosting should remain, but there should be optional support for paid hosting.

Some users of ZeroNet (hosts) might want to make money from hosting ZeroNet websites. So they set the ZeroNet program to hosting mode (this include setting the max amount of storage and payment address).

Then, the site owner decides to pay for hosting. He pays some amount of cryptocurrency (probably Bitcoin or Ethereum) to the network.

The network then decides how many (based on the amount that was paid) and which (randomly) hosts would serve the site. The site is then transferred to that hosts and hosts receive money for hosting.

## Considerations

- [ ] What should be the price for hosting.
It should depend on the amount of storage and the number of hosts.

- [ ] Which cryptocurrency should be used.
Bitcoin's cryptography is already used by ZeroNet.
Ethereum has some features that might be useful for this ([EIP 1337](https://1337alliance.com/) - subscriptions).

- [ ] How to implement payments.
This should be done with some subscriptions.
Hosts should be paid dynamically depending on how many sites and storage they host.

- [ ] How to implement hosts choosing.
There should be some good algorithm to choose the hosts.

- [ ] What if the host goes down.
Multiple hosts should be used for each site.
The host should not be paid when it is not hosting the site.
Hosts should be able to (temporary and permanently) go down.

## Existing projects

There are already some existing projects for distributed storage hosting. You could look to them for the idea how to implement this.

* [Storj](https://storj.io/)
* [Filecoin](https://filecoin.io/)
* Other "Proof of Storage" and "Proof of Capacity" projects

No files, tests, or entry points are identified in the issue. Start by reviewing the unresolved decisions around pricing, cryptocurrency, payment subscriptions, host selection, and host failure, along with the Storj and Filecoin references; the issue does not define what completion would look like.

Written by the indexing model from the issue text.