Wordle (word guessing game)

Implement the letter-scoring logic for a Wordle game.

Write function checkGuess(guess) that takes a 5-letter string and returns an array of { letter, color } objects:

• Green (#4CAF50) for correct letter in correct position
• Yellow (#FFC107) for correct letter in wrong position
• Gray (#9E9E9E) for incorrect letter

The target word is "REACT". Max 6 attempts.