Implement Smart Pipeline proposal in @babel/parser by mAAdhaTTah · Pull Request...

Q                      A Fixed Issues?Related to babel/proposals#29Patch: Bug Fix?NoMajor: Breaking Change?NoMinor: New Feature?YesTests Added + Pass?YesDocumentation PR LinkN/AAny Dependency Changes?LicenseMITMost of this work was implemented by the illustrious @js-choi, which some adjustments and refreshments from myself to use the new plugin options API. He's been fairly busy so I'm going to be working through the suggestions / changes here.This is a big PR, but it enables @babel/parser to parse the Smart Pipeline proposal's topic reference. As discussed in babel/proposals#29, this is the first step towards enabling the pipeline plugin to parse and emit all three proposals.Next, I'll be implementing F#-style parsing, then we'll work on the pipeline plugin itself. I want to get them in piece by piece to avoid merge conflicts. This work had drifted quit a bit, and took me a few days to refresh @js-choi's work with the latest from master, so I'd like to land each piece one by one.This is a pretty major chunk of work, so definitely interested in getting as much feedback as possible.?One step closer to the landing the pipeline proposals! ?cc @littledan Fix pipeline types (#8289 (comment)) Reuse tt.hash (if possible)