Improve error message for using ^ on boolean values

[sophiajt]

From #587 -

We should give a better, more helpful error message when the ^ operator is used on boolean values.

From the comment:

Given this decision, may I suggest improving the error message to state something akin to the following?

"error TS0000: The ^ operator is not allowed for boolean types. Consider using !== instead."

[chrisbubernak]

If no one is working on this already I'd like to give this a shot. I've spoken with @DanielRosenwasser and have a pretty good idea of how I want to tackle it.

[mhegazy]

thanks @chrisbubernak. go for it :)

[chrisbubernak]

This was fixed in pr #823.