Document release process

[shahankhatch]

• Update CONTRIBUTING.md
• Move relevant pieces from CONTRIBUTING.md to a new RELEASING.md
• Prepare checklist of tasks
• Prepare release notes template
• Include details of release/branch naming in order to trigger invariant checks
• Add reproducible build sha256 hashes to release notes
• Add reproducible build artifacts to release (build_report, and binaries)

Include following notes:

Commits go into main.

Check the replace line in go.mod file of the cosmos-sdk for something like:
https://github.com/cosmos/cosmos-sdk/blob/master/go.mod

replace github.com/gogo/protobuf => github.com/regen-network/protobuf v1.3.3-alpha.regen.1

And ensure that the latest version is also being used in Gaia.

Cherry-pick commits from main into the long-lived release/vn.n.x branch, e.g., release/v3.0.x. It’s also okay to create a long-lived branch from main if the last commit is the release commit.

Ensure you have checked out the commit you wish to tag.

git tag -a v3.0.1 -m 'Release v3.0.1'
-- optional, add the -s tag to create a signed commit using your PGP key (which should also be added to github)

Maybe do this before tagging:
git pull --tags --dry-run
git pull --tags

git push --tags --dry-run
git push --tags

Go to gaia repo and create a release from the newly minted tag.
Title: v3.0.1
Description: Release notes using the following template (see at the end of the doc for additional notes on potential changes to changelog management):

Gaia v.3.0.1 Release Notes
This release includes bug fixes from the Cosmos SDK and Tendermint.
This release also introduces important security patches.
No breaking changes are introduced, but users are encouraged to use this release when upgrading their networks to Gaia v3.
See the Cosmos SDK v0.40.1 Release for details.

make build-reproducable

[shahankhatch]

Perhaps add some notes on the ability to skip checks?
https://docs.github.com/en/github/collaborating-with-issues-and-pull-requests/about-status-checks