Public `setModifierManager` is not documented

[chriskrycho]

The merged RFC specifies a public import setModifierManager:

original RFC text

Ember will provide a new API to assign the modifier manager for a element modifier
class:

// my-app/app/modifier/foo.js

import EmberObject from '@ember/object';
import { createManager } from './basic-manager';
import { setModifierManager } from '@ember/modifier';

export default setModifierManager(createManager, EmberObject.extend({
  // ...
}));

// my-app/app/modifier/basic-manager.js

// ...

export function createManager(owner) {
  return new BasicManager(owner);
}

setModifierManager takes two parameters. The first parameter is a function that takes an Owner and returns an instance of a manager. The second parameter is the base class that applications would extend from.

Currently, setModifierManager is undocumented:

ember.js/packages/@ember/-internals/glimmer/lib/utils/custom-modifier-manager.ts

Lines 1 to 5 in ef3688b

	import { getManager, ManagerFactory, setManager } from './managers';
	export function setModifierManager(factory: ManagerFactory<unknown>, obj: any) {
	return setManager({ factory, internal: false, type: 'modifier' }, obj);
	}

We should document it!