feat: allow to sendTransaction and get TransactionReceipt

[troggy]

For the provider to work, leap-node requires to run this change: leapdao/leap-node#293

Then it should be possible to send transactions normally without hacks:

const LeapProvider = require('leap-provider');
const provider = new LeapProvider('https://testnet-node.leapdao.org');

// create some LeapTransaction
const tx = Tx.transfer(
  ...
);

// tx should be signed
tx.signAll(wallet.privateKey);

// send via provider
const resp = await wallet.provider.sendTransaction(tx);

// wait for inclusion, you will get a proper TransactionReceipt once tx is included in a block
const receipt = await resp.wait();
console.log(receipt);

Relates leapdao/leap-node#256

[sunify]

Nice!

[sunify]

Maybe use arrow function here as well?

[sunify]

Move ethers to peer deps may be a good idea to avoid double bundling for browser code

https://nodejs.org/es/blog/npm/peer-dependencies/#the-problem-plugins