feat(docs): add a RELEASE.md file

[cratelyn]

the release process for this repository was not documented.

this commit introduces a small release runbook.

Signed-off-by: katelyn martin git@katelyn.world

[cratelyn]

this is missing some steps.

i'm not sure what though, so i'll need some help from someone that does know what the release process for this repository is.

[olix0r]

The dev release process is fairly involved and manual currently. It typically works as follows:

1. In dev

• Create a branch in dev git co -b $(whoami)/v49
• First, update versions (i.e. with go run ./update-versions.go --in-place)
• just push=false version=v49 build -- build images
• just push=true version=v49 build -- push images -- note this publishes dev images
• In dev: replace all references to v48 with v49 -- especially in actions/setup-tools
• Ensure proper versions in actions/setup-go and actions/setup-rust
• git push origin $(whoami)/v49 -- so that you can reference the branch from other repos

2. In linkerd2-proxy (etc)

• Create a branch in that repo.

• Update devcontainer.json to use the new version, boot up the devcontainer and ensure your normal workflow continues working.

• Update all references to dev container images and actions. Update actions to reference the SHA of the dev branch during testing.

• Push a draft PR

• Repeat for all other repos.

  • Iterate as needed, publishing dev images and actions updates as needed.

3. In dev

• Merge PR that bumps versions.
• Publish a tag/release off of main once it is merged.

4. In other repos

• replace the SHA with the release tag
• move PRs out of draft
• merge