Bump Contributor Covenant to v3

[timgentry]

Summary

Bump the bundled Contributor Covenant Code of Conduct from v2.1 to v3.

Details

The project currently ships Contributor Covenant v2.1 (see CODE_OF_CONDUCT.md and the built-in feature template at lib/way_of_working/code_of_conduct/contributor_covenant/templates/docs/way_of_working/code-of-conduct.md).

Contributor Covenant v3 is now available. We should update to the latest version.

Tasks

• Update CODE_OF_CONDUCT.md to Contributor Covenant v3
• Update the built-in feature template under lib/way_of_working/code_of_conduct/contributor_covenant/templates/
• Update version references and links (currently pointing at version/2/1/)
• Update CHANGELOG.md

References

• Contributor Covenant: https://www.contributor-covenant.org/