Support keynet via tor js

[voltrevo]

Basic test (UPDATE: keynet service no longer available):

// test.ts

import { JsonRpcProvider } from './src.ts'

(async () => {
    const provider = new JsonRpcProvider('http://jyn6dehf3ttu4lblc7tr3i23xqsz76dn2du6keptg5kyo3r6mur36vad.keynet/ethereum')
    const blockNo = await provider.getBlockNumber();

    console.log(blockNo);
    process.exit(0);
})().catch(e => {
    console.error(e);
    process.exit(1);
});

dev-vm ➜ ethers.js git:(support-keynet-via-tor-js) ✗ npx tsx test.ts
NOTICE: tor-js is experimental software: https://github.com/voltrevo/tor-js/issues/4
24065513

Before merging/releasing this, we should probably fix:

• wss://snowflake.pse.dev is hardcoded as the snowflake bridge
  • (This can be changed with tor.configure but that's not exposed in the ethers api)
  • I believe the plan is for there to be a few of these hosted by commercial RPC providers
  • tor-js should be configured with all of them, randomize, and do failover

That will not change this PR very much though, so I'm hoping we can sync on expectations and get a tentative OK here :)

[voltrevo]

I've taken down the keynet service in the example to save costs. Let me know if you'd like me to create a new one.