Function ofArrayMutable

ofArrayMutable<V>(
options?: MapArrayOpts<V>,
): IMapOfMutableExtended<V, readonly V[]>
Returns a IMapOfMutableExtended to allow storing multiple values under a key, unlike a regular Map.
Type Parameters
- V
  Data type of items
Parameters
- options: MapArrayOpts<V> = {}
  Optiosn for mutable array
Returns IMapOfMutableExtended<V, readonly V[]>
IMapOfMutableExtended
Example
```
const map = ofArrayMutable();
map.addKeyedValues(`hello`, [1,2,3,4]); // Adds series of numbers under key `hello`

const hello = map.get(`hello`); // Get back values
```
Takes options:
- comparer: IsEqual
- toString: Util.ToString
A custom Util.ToString function can be provided as the convertToString opion. This is then used when checking value equality (has, without)
```
const map = ofArrayMutable({ convertToString:(v) => v.name}); // Compare values based on their `name` field;
```
Alternatively, a IsEqual function can be used:
```
const map = ofArrayMutable({comparer: (a, b) => a.name === b.name });
```