Add instructions

Author: ajeetdsouza

README.md

@@ -20,3 +20,25 @@ go install github.com/ajeetdsouza/clidle
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 </div>
+
+## How to play
+
+You have 6 attempts to guess the correct word. Each guess must be a valid 5 letter
+word.
+
+After submitting a guess, the letters will turn green, yellow, or gray.
+
+- **Green:** The letter is correct, and is in the correct position.
+- **Yellow:** The letter is present in the solution, but is in the wrong position.
+- **Gray:** The letter is not present in the solution.
+
+Your final score is based on how many guesses it took to arrive at the solution:
+
+| Guesses | Score |
+| ------- | ----- |
+| 1       | 100   |
+| 2       | 90    |
+| 3       | 80    |
+| 4       | 70    |
+| 5       | 60    |
+| 6       | 50    |