Show the limit of sats that can be exchanged

[Catrya]

Some users report that their orders are not created, and that is a bad UX that makes many not try to use Mostro again. Most of the time it happens because they try to create an order outside the range allowed by Mostro, because they do not know the allowed limits.

I suggest putting up some kind of notice showing what the current limits are to avoid these kinds of issues.