[FEATURE REQUEST]: custom message when sending one-time payment

[sidvishnoi]

Describe the feature you would like to request

Consider adding an optional custom text field under amount to let payer specify a custom message when sending money. Wallets can display it in transactions list.

Describe the solution you would like

Specify a "standard" metadata field for payment description.

Additional context

Suggested by @theadz during WM community call.