Request to add Dafny's <==> operator

[LenaWil]

Dafny's iff operator looks like this: <==>. However, in Firacode, it either looks like ≤> or <⟹, depending on the IDE. Is it possible to add an operator?

[LenaWil]

I see I overlooked #346, so feel free to close this one.

[tonsky]

This one would be faster to add. Where is it used?

[LenaWil]

It's an operator in Dafny that is almost the same as ==, but only works with booleans, like this:

method testMethod() {
    assert true <==> true;
}

[tonsky]

Oh, I see. I thought that it was the name of the operator :)

[tonsky]

It seems that this is already in the font since 1.206 (see #392). Check your font version