games/mastermind: traditional console-based mastermind game

This is a traditional console-based Mastermind game. The rules are as follows:

1. The game will generate a 4-digit color/number code
2. The range of colors/numbers is from 1 to 8
3. The player has 10 chances to guess the code
4. After each guess, the system will provide hints:
   • Green plus sign (+) indicates both color and position are correct
   • Red minus sign (-) indicates the color is correct but the position is wrong
5. The player needs to gradually guess the correct code based on the hints
6. During the game, you can enter 'r' at any time to switch display mode (color blocks/numbers)
7. During the game, you can enter 'q' at any time to exit the game

WWW: https://github.com/bigdragonsoft/mastermind