Tic-tac-toe: Explicit the game's independence from user input

[nekosoffy]

Because

Because they imagine a person playing tic-tac-toe, students usually think that they require something to take their input (prompt) for the game to work (like they did in RPS), which isn't true. I think a reminder that this isn't needed at all would be useful so that they don't have to refactor the code when they reach the DOM stage because they introduced an unneeded step earlier.

This PR

• Adds a reminder to the project's instruction about how it's possible to test the parts of the game by passing arguments to functions instead of taking user input.

Issue

Closes #XXXXX

Additional Information

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