Add proper logic for yellow letters

[kav2k]

Follows proper Wordle logic for misplaced guesses, fixes #2

[kav2k]

Oops, I need to double-check this. Edit: yes, nevermind, the logic is completely wrong, need to rewrite.

[kav2k]

Okay, I'm just paranoid. It seems to work fine after some testing.

The rules are as follows:

• Highlight exact guesses as green.
• Go over non-highlighted letters, left to right. Highlight yellow if:
  • Is in the target word
  • The total number of highlighted instances of this letter is not greater than total number in the target word

Algorithm is as follows:

• If the guess letter is an exact match, it's not yellow (it's green)
• Otherwise, count the number N of occurrences of that letter that aren't exactly matched in the target word.
• Then, count the number M of occurrences of that letter that aren't exactly matched in the part of guess before current index.
• If M < N, then it's yellow, otherwise do not highlight (because the total would be more than in the target).

[kav2k]

Examples of it working (with a "cheat" of the intended word being visible)