Adding documentation of BidirectionalPort

[Ale-Amici]

Hello,
I always forget what is the name of BT::BidirectionalPort, I try out BT::InputOuput or other similar alternatives.
There is no documentation on the tutorials or in general in the behaviortree.dev website.

I wonder, is their use discouraged?
If not, I think they should be mentioned in tutorials and other documentations about ports :)

[facontidavide]

No it is not discouraged.