#93 Material Design Icons license changed to Apache 2.0

The title says it all, but the license of [Google's Material Design Icons](https://github.com/google/material-design-icons) (§Graphics, §§Icons) has changed to the [Apache License, version 2.0](https://www.apache.org/licenses/LICENSE-2.0).

Fixed in https://notabug.org/Calinou/awesome-gamedev/commit/9dfbab2494517d49f53a8ea13a58f3fa2760b80a.