[IDEA] Add Export/Import Step to Transformers

[rogin]

Is your feature request related to a problem? Please describe.
I'm migrating popular requests from NextGen's repo. This was issue nextgenhealthcare/connect#5276

JeffBendict's exact comment: I know that many folks use pure javascript in their transformers, but in some cases starting out using Mapper and Message Builder steps in a transformer are easier to wrap one's head around and use; but a caveat to using them is that they are not easily transferable from channel to channel. It would be nice if there was an Export/Import Step(s) option. This would make it almost as easy as doing a Copy/Paste for JavaScript. I know you can Export/Import the entire Transformer, but what if I just want a single step from a transformer with multiple steps? It would be nice to be able import a particular step from a transformer w/o having to append the entire thing and then remove the steps you don't want.