Automate Node.js Release PRs

[darcyclarke]

Problem statement

Currently our process for opening a pull requests against the Node.js Project is almost entirely manually done post-release; Letting computers do the work here will save developer time & mindshare as well as reduce complexity or potential for human error.

Features

• a GitHub Action kicks off & generates a pull request for npm cli releases
• the correct staging branch or branches* are targeted (ex. v15.x, v14.x, v12.x etc. release lines)
• the correct PR title & description are generated from the changelog (ex. https://github.com/nodejs/node/pulls?q=is%3Apr+is%3Aclosed+npm+label%3Anpm)

Exit criteria

• feature-set fully implemented/functioning
• release process/documentation is updated
• Node.js Release WG is made aware of the changes to our process

Useful Links

• Release WG
• Our Current Release Process
• Node.js Maintaining npm Guide