Disabled buy or sell button state after pressing and waiting for the wallet signature

[matt-bullock]

This is to prevent the user from buying twice as well as giving feedback as there can sometimes be a long delay before the wallet signer appears

https://www.figma.com/file/6y4nvjfeVZwzwKcoXB0neq/Simplified-UI?node-id=2287%3A589

• Disable button and add the button text shown below
• on mobile the betslip should disappear once the transaction has been signed