Prepare initial SvelteKit SDK Alpha release

[Lms24]

### Before release
- [x] Ensure we have unit tests for the SK-specific SDK features
- [x] Ensure README has an "Alpha state" note 
- [ ] https://github.com/getsentry/sentry-javascript/pull/7490
- [ ] https://github.com/getsentry/sentry-javascript/pull/7507
- [x] Follow "New SDK Release Checklist" to ensure all necessary files are in place and the release/publish setup is configured
- [x] Prepare Release registry PR (https://github.com/getsentry/sentry-release-registry/pull/103)

### After release
- [x] Add `@sentry/sveltekit` to the release registry (merge https://github.com/getsentry/sentry-release-registry/pull/103)
- [x] Reach out to community with feedback request