Who're.
Contractions are always informal - they are governed by rules no more strict than slang or colloquialisms. In fact, some contractions are colloquial. To claim that a contraction is unrecognised, especially one that is often used in spoken English, would be arrogant.
Other contractions include:
you're
we're
they're
Remember, the English language has its own set of rules and there are so many exceptions, the only important thing to do is memorize the correct spellings and word forms.
There is no contraction. The contraction we're means "we are."
There is no contraction for I was. There is a contraction for I am (I'm) and for I have (I've).
There is no contraction of we'll. It is a contraction, meaning "we will."
There is no contraction. The word isn't is the contraction, meaning "is not."
There is no contraction. There is a contraction we'dmeaning either we would or we had.
There is no contraction for were you. There is no contraction for you were.There is a contraction for "you are" (you're).
There is no contraction for "its not."There is a contraction for "it is" (it's).There is a contraction for "is not" (isn't).
He's already IS a contraction. It is a contraction of he is.
It's is the contraction of it has and it is.
There is no contraction. There is a contraction doesn't which means "does not."
There is no contraction for I was. There is a contraction for I am (I'm) and for I have (I've).
There is no contraction. The contraction we're means "we are."
The contraction for he will is He'll
We're is a contraction of we are.
"They've" is the contraction for 'they' and 'have'.
The grammatical contraction for "have not" is "haven't."
Didn't is a contraction of the words "did" and "not". There is no 'contraction' for this word.