utils.appendChild mutates child fragment

[pgoldrbx]

When calling utils.appendChild with a child fragment, the fragment is mutated, resulting in an empty array.

const jml = ['div'];
const fragment = ['', 'hello world'];
utils.appendChild(jml, fragment);
// jml === ['div', 'hello world']
// fragment === []

Ideally, the fragment should not be mutated.
See discussion: #5 (comment)