Add deeper guidance on lightning fee controls

[Bosch-0]

Wallets like Phoenix and Breez have some extra settings when it comes to managing lightning fees such as setting a max amount you want to pay for a payment. We should incorporate some of the below content into the guide.

[GBKS]

I like this idea. I've found there's a lack of transparency around fees. Certain other well-known wallets don't even let you see what the fees were for a payment and you have to figure it out by subtracting the invoice amount from what was actually deducted from your balance.

[pavlenex]

Talked to quite a few people lately, and most of their confusion around the wallets was indeed fee transparency. "Why does this wallet charge sometimes X and sometimes Y, and why is Z wallet 3 times the fees than Q wallet?"