Add a faucet for testnet3 and testnet4 coins

[GitGab19]

We should add a faucet on our website to distribute testnet coins mined during our testings.

Here a list of resources that I found:

• bitcoin-faucet in node.js: https://github.com/jprichardson/bitcoin-faucet
• recaptcha for vue.js: https://dansnow.github.io/vue-recaptcha/guide
  • npm module: https://www.npmjs.com/package/vue-recaptcha

[pavlenex]

Not convinced this should be on this website, but let's see what others think. There are way more higher priority tasks for this repo than this one, that's for sure.