Automate release process via Changesets

[ernestognw]

Description

This PR is aiming to automate the release process by adding the following changes:

Tasks

• Add Changesets Configuration for CHANGELOG.md management
• Use Changeset Action for automating Release Pull Requests
• Post-processing for the CHANGELOG.md, so it aligns with our current format (changesets don't fully support customization)
• A Github Actions Workflow for the release cycle that reacts to the current state of a release branch
• An Isolated GitHub Action for publishing to NPM
• A Github Action to detect when a Pull Request doesn't include a Changeset
• An action to Open a Pull Request back to master and merging changesets history after cherry picks
• Convert Unreleased changes to Changesets
• Test complete workflow in a fork of OpenZeppelin Contracts (requires publishing)

Release Cycle

stateDiagram-v2
	a: master
	b1: Unreleased Prerelease
	b2: Ready Prerelease
	c1: Ready Final Release
	c2: Patched Final Release 

	prerelease: Release Candidate
	state prerelease {
	  b1 --> b2: Merge Changesets PR
    b2 --> b1: Cherry pick fix from master
  }

 	release: Final Release
  state release {
    c1 --> c2 : Merge Changesets PR
    c2 --> c1 : Cherry pick patch from master
  }
	
	a --> b1 : Manual Dispatch
	b2 --> c1 : Manual Dispatch

	note left of prerelease
		Publish each ready prerelease as a release candidate
  end note

  note left of release
		Publish each ready release as patch
  end note

Required Changes

In order to implement the automation, it was needed to first adapt some things:

• Adapt CHANGELOG.md format to use prettier (that's the default for changesets)
• Add missing dates to CHANGELOG.md so the new format-changelog.js script doesn't override them
• Update PULL_REQUEST_TEMPLATE.md to use changesets
• Remove git interactions from npm run version, now the Changesets PR adds them all to a PR

TODO before merging

Since this Pull Request interacts with some GitHub repository settings, it's needed to first configure the following:

• Add an npm environment
  • Should include NPM_TOKEN variable
  • Should include reviewers
• Configure changesets bot

Open Questions

• The Changeset Action doesn't include an input to override description, which is returning the full CHANGELOG.md due to the post-processing we do in format-changelog.js
• The Release Cycle workflow creates a Github Release but it requires a Changelog section, and I'm not sure how to pick it up

[ernestognw]

@frangio I took your RegExp comments with some small modifications, you can review it again but I wouldn't suggest that since there are a few things to consider:

1. Each replace line modifies the content of the Changelog, some regex may affect other's inputs
2. Each replace line MUST NOT modify old content, so we have to be careful on putting expressions that might match previous releases (that's why relying on \[.)
3. A line of content interacts with more than other lines (eg. matching ^(- .*\n)\n(?=-)/mg doesn't match if a title is below that particular line, also consider minor/major/patch lines should be removed first in that case)

I tested with multiple files I have in the history of this PR and it works fine, but I don't want to focus on hyper optimize this RegEx since it may break discoveries I made in the past while testing.

Pending changes

[frangio]

Suggested change

	name: Changesets PR
	name: Update PR to release

[frangio]

Suggested change

	name: Release PR back to master
	name: Create PR back to master

[frangio]

Looks good!

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