Add Option for Custom Network Fee on send-btc CLI Command

[ronaldoguedess]

I would like to propose an enhancement to the send-btc CLI command to allow users to specify a custom network fee. This would provide greater flexibility and control over transaction costs.

Current Command:
npx hardhat send-btc --amount 0.0001 --memo

Proposed Enhancement:
px hardhat send-btc --amount 0.0001 --memo xxxxxxx --fee 100

Additional Notes:

• The --fee parameter should accept an integer value representing the fee in satoshis (sats/vBytes).
• Consider adding documentation and examples for the new --fee parameter.

[fadeev]

Good suggestion! Thanks for creating an issue for this.