message: Add annotation example in CircleCI plugin README
  * Add annotation example in CircleCI plugin README
  Closes
  * Specify lang for highlighting
diff: @@ -50,7 +50,7 @@ import { Router as CircleCIRouter } from '@backstage/plugin-circleci';
  4. Add proxy config:
  -```
  +```yaml
  // app-config.yaml
  proxy:
  '/circleci/api':
  @@ -63,6 +63,19 @@ proxy:
  5. Get and provide `CIRCLECI_AUTH_TOKEN` as env variable (https://circleci.com/docs/api/#add-an-api-token)
  6. Add `circleci.com/project-slug` annotation to your component-info.yaml file in format <git-provider>/<owner>/<project> (https://backstage.io/docs/architecture-decisions/adrs-adr002#format)
  +```yaml
  +apiVersion: backstage.io/v1alpha1
  +kind: Component
  +metadata:
  + # ...
  + annotations:
  + # This also supports bitbucket/xxx/yyy
  + circleci.com/project-slug: github/my-org/my-repo
  +spec:
  + type: service
  + # ...
  +```
  +
  ## Features
  - List top 50 builds for a project
  