[v1.8.0] Macro bundles and Reader/Writer API

API additions

• #56 Flesh out Reader and Writer APIs by @joroKr21

Macro changes

• #53 Refactor to use macro bundles by @joroKr21

Build changes

• #55 Add MiMa binary compatibility validation by @joroKr21

Dependency updates

• #54 Update scalatest to 3.2.2 by @moia-pipeline
• #57 Update sbt-mima-plugin to 0.8.0 by @moia-pipeline
• #58 Update scala-collection-compat to 2.2.0 by @moia-pipeline
• #59 Update sbt to 1.4.0 by @moia-pipeline