Add License Header inside .js & .min.js file

[mikeploeger]

Could you please add a license header inside your library material-avatar.js & .min.js file?
Otherwise the license notice, which is required by the MIT License you choose, isn't included automatically and must be added manually.

Thanks!

[mikeploeger]

If you want I could also do a PR

[hellsan631]

i love a pr for this