migrate to pnpm

[marcalexiei]

• Closes Migrate to pnpm #110

Change repository package manager to pnpm

Since there was already a mention of yarn in the README "Setup" section,
I used this PR to make a few documentation improvements:

• Moved setup documentation from README.md to a new CONTRIBUTING.md
• Moved the install URL into the relevant section body
• Removed a duplicate screenshot
• Added a ## Changeset format heading before the changeset file format example paragraph

[vercel]

@marcalexiei is attempting to deploy a commit to the Changesets Team on Vercel.

A member of the Team first needs to authorize it.

[socket-security]

Review the following changes in direct dependencies. Learn more about Socket for GitHub.

Diff	Package	Supply Chain Security	Vulnerability	Quality	Maintenance	License
	@​types/​js-yaml@​3.12.5 ⏵ 3.12.10			+1
	@​changesets/​types@​6.0.0 ⏵ 6.1.0	+1		+1
	@​types/​micromatch@​4.0.1 ⏵ 4.0.10			+1
	@​changesets/​config@​3.0.1 ⏵ 3.1.4			+1
	@​types/​node@​12.12.29 ⏵ 25.6.2			+2	+1
	js-yaml@​3.14.1 ⏵ 3.14.2		+2
	vite@​8.0.10 ⏵ 8.0.11			+1
	@​changesets/​parse@​0.4.0 ⏵ 0.4.3			+2
	micromatch@​4.0.2 ⏵ 4.0.8	+1	+2
	@​changesets/​assemble-release-plan@​6.0.2 ⏵ 6.0.10			+1
	@​octokit/​webhooks@​9.26.0 ⏵ 9.26.3		+16
	probot@​12.2.4 ⏵ 12.4.0	+1	+16	+1
	oxlint@​1.62.0 ⏵ 1.58.0				+1
	msw@​2.12.14 ⏵ 2.14.5
	knip@​6.11.0 ⏵ 6.12.1	+1		+1

View full report

[Andarist]

The deployment failed with:

Running build in Washington, D.C., USA (East) – iad1
Build machine configuration: 4 cores, 8 GB
Cloning github.com/changesets/bot (Branch: master, Commit: ea5e300)
Cloning completed: 259.000ms
Skipping build cache since Package Manager changed from "yarn" to "pnpm"
Running "vercel build"
Detected `pnpm-lock.yaml` 9 which may be generated by pnpm@9.x or pnpm@10.x
Using pnpm@9.x based on project creation date
To use pnpm@10.x, manually opt in using corepack (https://vercel.com/docs/deployments/configure-a-build#corepack)
Installing dependencies...
 ERROR  packages field missing or empty
For help, run: pnpm help install
Error: Command "pnpm install" exited with 1

I'll look into it in following days but if you'd found the time to investigate what has to be done here, I'd greatly appreciate it.