feat(angular): Expose custom browserTracingIntegration

[mydea]

This way, Angular users do not need to provide a routingInstrumentation but can just import & use this directly from their angular package.

New usage:

import * as Sentry from '@sentry/angular';

Sentry.init({
  dsn: '__DSN__',
  integrations: [
    Sentry.browserTracingIntegration({
      tracingOrigins: ['localhost', 'https://yourserver.io/api'],
    }),
  ],
  tracesSampleRate: 1,
});