Updating upgrade helper

Point people: @lucasbento, @pvinis, @kelset_

From the readme of its dedicated repo:

The Upgrade Helper tool aims to provide the full set of changes happening between any two versions, based on the previous work done in the rn-diff-purge project:

This repository exposes an untouched React Native app generated with the CLI react-native init RnDiffApp. Each new React Native release causes a new project to be created, removing the old one, and getting a diff between them. This way, the diff is always clean, always in sync with the changes of the init template.

The upgrade helper webapp relies on rn-diff-purge having the diff for the versions of RN released.

To generate the diff for a new version, there are essentially just 3 steps needed:

• git clone the rn-diff-purge repo
• cd into it, and yarn install
• run the script ./new-release.sh <version_tag>, so for example ./new-release.sh 0.66.0-rc.1
  • to run this successfully, you need to have write access/be a Code Owner for the repo; else, one of the last steps will fail since main is a protected branch.