import { newTracker } from '@snowplow/browser-tracker';
import { SimpleContextTemplate } from 'snowplow-browser-plugin-simple-template';

newTracker('sp1', '{{collector}}', { plugins: [ SimpleContextTemplate() ] });

Assuming sp.js or sp.lite.js has been loaded on window.snowplow, and this plugin is published on npm:

window.snowplow('addPlugin', 
  "https://cdn.jsdelivr.net/npm/snowplow-browser-plugin-simple-template@latest/dist/index.umd.min.js",
  ["snowplowSimpleTemplate", "SimpleContextPlugin"]
);