Only mark letters without matches

Fixes #7 (closed)

Instead of checking if each letter guess is in the correct, make a copy of the correct word, and remove from the copy each match

• Find exact matches:

.	.	.	.	.	.
correct	C	R	E	D	S
written	C	R	E	E	D

• Then check the remaining letters

.	.	.	.	.	.
correct				D	S
written				E	D

With the current algorithm the result is 🟩🟩🟩🟨🟨, which is wrong because the correct word only has one E. With this new one it would be 🟩🟩🟩⬛🟨 like in the original game