Per the header comment for the file under review here:

  OpenTelemetry is a complex project with many moving parts. Thankfully,
  we strive to keep those parts loosely coupled where we can (this has
  been a goal since the very announcement of OpenTelemetry, per this blog
  post: https://medium.com/opentracing/merging-opentracing-and-opencensus-f0fe9c7ca6f0)

  This file describes the structure of the project and its
  sub-components, definitions of API and stability maturity levels, and
  finally records the current maturity of each component. We maintain
  this file as YAML in order to make it easier to automate scripts
  (e.g., for the website) that present the data to OpenTelemetry
  end-users.

add golang status, add additional states.