add docs for injectLocalStorage

[eneajaho]

Looks like docs weren't added when the utility was created https://github.com/ngxtension/ngxtension-platform/blob/main/libs/ngxtension/inject-local-storage/src/inject-local-storage.ts

[eneajaho]

Docs here: https://ngxtension.netlify.app/utilities/injectors/inject-local-storage/

[sysmat]

docs are missing from where to import injectLocalStorage

import { injectLocalStorage } from 'ngxtension/inject-local-storage';