Add Sparrow as a recommended wallet in FAQ Gap limit solution.

[Bas02]

We should look at the wallet around and see if there's more to add here;

"The only wallets that allow gap-limit configuration, that we're aware of are Electrum and Wasabi"

On page ; https://docs.btcpayserver.org/FAQ/Wallet/#the-gap-limit-solution

AFAIK Sparrow wallet also allows it ; https://github.com/sparrowwallet/sparrow/issues/10#issuecomment-689545787