setup some release stuff

[threepointone]

Mostly copied from workers-oauth-provider. I still need to setup repo secrets and a couple of apps, but opening this rn.

EDIT: added secrets and apps.

---

This sets up some stuff for release automation, built around github actions, changesets, and pkg.pr.new.

• pkg-pr-new.yml: For every pull request, we publish a version to their registry, and a comment will popup in the PR comments showing how to use it (eg: Add codeVerifier in TokenExchangeCallbackOptions workers-oauth-provider#99 (comment)) This lets people test out PRs before they even land.
• prerelease.yml: whenever something lands in main, after Test(test.yml) passes, we publish to npm with @beta, with the version being the git hash. This lets people test whatever's in master quickly.
• release.yml: When a PR lands after Test(test.yml) passes, the changeset action opens a Version Packages PR (if not already created), that deletes all changesets under the .changeset folder, and populates the CHANGELOG with their contents. You can edit the CHANGELOG further as you wish here.
• release.yml: When the Version Packages PR itself lands, then the changesets action will do an npm release (with the highest common changeset level: path, minor, or major). It will also tag git and make a github release.

You can make a changeset in 2 ways:

• running npx changeset in your PR branch, which will ask you a couple of questions (what level of change, and title). You can add more details directly in the generated changeset. You can add as many (or as few, even 0) changesets as you'd like.
• Every PR will have a comment generated that shows what changesets are included (or if they're not). This will also have a link to generate and add a changeset to the PR directly (example Add codeVerifier in TokenExchangeCallbackOptions workers-oauth-provider#99 (comment))

[changeset-bot]

🦋 Changeset detected

Latest commit: aec9092

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
capnweb	Patch

Not sure what this means? Click here to learn what changesets are.

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

[pkg-pr-new]

Open in StackBlitz

npm i https://pkg.pr.new/cloudflare/capnweb@100

commit: aec9092