Update readme & setup

[mydea]

While trying to get this to run from scratch, I noticed some things with the readme/setup docs, so I figured I'd update everything to make sure it's easy to run this:

1. Mention that you need to install pre-commit
2. put SENTRY_PROJECT into example .env + update to recommend org auth tokens
3. Add command to create categories
4. Remove unneeded package-lock.json (we are using pnpm here)
5. avoid using pnpx, just use npx (pnpx didn't work for me, I guess I'd need some more pnpm setup for this, but probably npx is just fine here)
6. do not run npx prisma db seed ?? (this complained that there is no seed configured, not sure if I missed this somehwere?)

[codecov[bot]]

Codecov Report

Attention: 14 lines in your changes are missing coverage. Please review.

Files	Coverage Δ
app/models/category.server.ts	83.33% <6.66%> (-16.67%)	:arrow_down:

:loudspeaker: Thoughts on this report? Let us know!.

[bruno-garcia]

Remove unneeded package-lock.json (we are using pnpm here)

Broke GCP build because:

https://github.com/getsentry/vanguard/blob/aa3e972ed3a409321a1697a0f207e2c82ba6bab5/Dockerfile#L21-L22

I'll try to remove that and we'll see (not sure how pnpm work) if that does it