v0.27.0

What's Changed

• docs: add RELEASING.md by @nielspardon in #146
• feat: remove generated protobuf code from substrait-python by @vbarua in #145

Breaking Changes

• code under substrait.gen.proto is now found under substrait
• simple extension files have been moved from extensions to extension_files
• version information has been moved to substrait.version module

Full Changelog: v0.26.0...v0.27.0