[RFC #0078] - Group additions to builder order

[natalieparellano]

RFC #0078 - Group additions to builder order

Spec:

• Group additions to Builder order spec#233
• Released in Project Descriptor API version 0.2

Pack:

• RFC: Support build.pre.buildpacks build.post.buildpacks in project.toml pack#1100 (project.toml)
• RFC-0078 Support for --pre-buildpack and --post-buildpack pack#1621 (flags)
• Released in pack version 0.29.0

Documentation:

• https://github.com/buildpacks/docs/issues/

Maintainers: when closing this issue as completed, submit a PR to update the Status of the RFC to Implemented.