Right now, this textobject only looks for pairs that surround the
cursor. This ensures that the pair found encloses each selection, which
is likely to be intuitively what is expected of this textobject.

Co-authored-by: Michael Davis <[email protected]>

Prior, it was missing the case where the start of the selection came
before the opening brace. We also had an off-by-one error where if the
end of the selection was on the closing brace it would not work.