message: Fix typo in README.md
  `Perfromance` => `Performance`
diff: @@ -83,7 +83,7 @@ development. If you're thinking about contributing to or creating a JavaScript-b
  below:
  - [`@sentry/tracing`](https://github.com/getsentry/sentry-javascript/tree/master/packages/tracing): Provides Integrations and
  -extensions for Perfromance Monitoring / Tracing
  +extensions for Performance Monitoring / Tracing
  - [`@sentry/hub`](https://github.com/getsentry/sentry-javascript/tree/master/packages/hub): Global state management of
  SDKs
  - [`@sentry/minimal`](https://github.com/getsentry/sentry-javascript/tree/master/packages/minimal): Minimal SDK for
  