fix: correct create type definitions

[nikku]

Add (optional attrs) in all cases.

Return SVGElement instead of Element as an escape.

---

The following would otherwise return Element, which is an entirely wrong type (i.e. does not support dataset and friends:

import { create } from 'tiny-svg';

const svg = create('svg', { fill: 'blue' });

svg.dataset; // non-existing according to type checking