Don't let the player make obviously incorrect guesses

[mh120888]

As a player, I don't want to be able to accidentally make a guess with a word that doesn't contain exactly 5 letters.

Definition of done:

• If a player attempts to make a guess with fewer than 5 letters, they should see a message saying "Not enough letters" and the guess does not count.
• A player should not be able to enter more than 5 characters for a single guess.