Add Undo Last Move Feature

[bhumishah2411]

Allow user to go back one move.

Acceptance Criteria:

• “Undo” button
• Stores previous grid + score
• Restores correctly
• Disabled if no previous move

[ManshaAgarwal716]

Hello @bhumishah2411 ,
I would like to work on this issue would you please assign it to me.