Add next major to release workflow

[colebemis]

Motivation

We want to reduce the frequency of major releases of @primer/react without slowing down the release cadence of minor and patch releases.

Solution

This PR implements workflow changes that allow us to merge breaking changes into a next-major branch (instead of main) that can be tracked and released independently of minor and patch versions.

[changeset-bot]

⚠️ No Changeset found

Latest commit: 7bd0f95

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

This PR includes no changesets

When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types

Click here to learn what changesets are, and how to add one.

Click here if you're a maintainer who wants to add a changeset to this PR

[github-actions]

size-limit report 📦

Path	Size
dist/browser.esm.js	64.24 KB (0%)
dist/browser.umd.js	64.6 KB (0%)

[jonrohan]

If this nice workflow diagram is intended to stay in docs somewhere, there's one small update to this block

Create branch called 'next-major' from 'main' branch

[jonrohan]

Nice, this has generally worked for us in primer/css. 👍🏻

[jonrohan]

Suggested change

	- 'changeset-release/main'
	- 'changeset-release/next-major'
	- 'changeset-release/**'

Not necessary but these could be **

[colebemis]

I wanted to be explicit here because I'm referencing those branch names directly in the workflow if statements