[Svelte] onMount doesn't have to be defined/called specifically in the component

App.svelte

<script>
	import mountIt from './mountIt';

  mountIt(); // logs when the component is mounted. Must be called in the component's script tag, during initialization.
  // if you want to get a value out of the onMount, you could use promises, reactive declarations, stores, etc.
</script>

mountIt.js

import { onMount } from './onMount';

function mountIt() {
  onMount(() => {
    console.log('the component has mounted');
  });
}

export default mountIt