Add reject() function for wallets.

[chudilka1]

Is there a chance to get a reject() function added for Wallet that would reject the transactions (the opposite of approve())?

[osis]

Yes! Should be an easy addition and I wonder why it hasn't come up before. 🤔

Should be a very easy PR for anyone to contribute. 🙌

[alejogranerorequest]

Hey @osis , could you develop it? It is very useful

[osis]

Will take a look at it during the next slot of time. Should be an easy one for anyone to pick up though if it's urgent.

[osis]

implemented in #280