Percentage of total wallet funds to exchange
![Screenshot_20240407-125403](https://github.com/cake-tech/cake_wallet/assets/50528556/44a088f2-07a1-416e-b8f9-fd9297f90303)

Could be nice if you could ex. exchange 50% of your btc to xmr instead of having to manuelly calculate total funds.

Example from guarda wallet in the screenshot.

