vanieth should check vanity address characters are valid ([:digit:abcdef])

[igponce]

Running vanieth with characters that cannot be part of an Ethereum address should return an error.

For instance, running:

$ vanieth feo -n25

should return an error. It could even suggest a substitution:

$ vanieth feo -n25
vanieth feo
           ^
Error: 'o' is not a valid character for Ethereum addresses. Did you mean '0' ?

[igponce]

(can you please assing this issue to me ? ;-)

[makevoid]

yes it would be a nice feature to have :)

if no one does a PR for this it I will code it at some point

[igponce]

PR Sent!

I didn't coded the suggestion :-( and there are a lot of cases where you can specify a regex that will never match an ethereum addres; but at least the CPU won't be red hot looking for a substring that cannot be part of an address.