Update rock-paper-scissors game

[Srish-ty]

The errors and bugs we found :

• There wasn't any error handling for invalid selection.
• if user chooses more than 2, the code crashes with error, index out of range.
• the game could be played only once

Changes and features we've introduced :

• Handled errors.
• If chosen invalid selection or out of range number, code asks user to input again, instead of crashing code.
• game can be played multiple times in a row
• until user wants to quit. Then they'll have to type q

Have a look at the game after these changes, We hope you'll like it.