Update interface in TS

[laurentmmeyer]

AFAIK this TS interface doesn't cover if you add an element to wrap like in the readme:

  <Typed
                strings={[
                    'Search for products',
                    'Search for categories',
                    'Search for brands']}
                    typeSpeed={40}
                    backSpeed={50}
                    attr="placeholder"
                    loop >
                    <input type="text"/>
                </Typed>

That should fix it.