Function helper

helper<T = unknown, S = InferSignature<T>, Return = Get<S, "Return", unknown>>(
    context: object,
    helper: T,
    thunk?: Thunk,
): { value: Return }
implemented with raw invokeHelper API, no classes from ember-resources used.

Enables the use of template-helpers in JavaScript

Note that it should be preferred to use regular functions in javascript whenever possible, as the runtime cost of "things as resources" is non-0. For example, if using @ember/component/helper utilities, it's a common p practice to split the actual behavior from the framework construct
```
export function plainJs() {}

export default helper(() => plainJs())
```
so in this case plainJs can be used separately.

This differentiation makes less of a difference since plain functions as helpers will be supported soon.
Type Parameters
- T = unknown
- S = InferSignature<T>
- Return = Get<S, "Return", unknown>
Parameters
- context: object
- helper: T
- thunk: Thunk = DEFAULT_THUNK
Returns { value: Return }
Example
```
import intersect from 'ember-composable-helpers/addon/helpers/intersect';

import { helper } from 'reactiveweb/helper';

class Demo {
  @tracked listA = [...];
  @tracked listB = [...]

  intersection = helper(this, intersect, () => [this.listA, this.listB])

  toString = (array) => array.join(', ');
}
```
```
{{this.toString this.intersection.value}}
```
- Defined in helper.ts:58