Add a license

[wkevwang]

Thanks so much for your implementation! It's been really helpful for understanding HED. Could you add a license for the code? That would make it more clear what you allow others to do with your code.

[xwjabc]

Could you add a license for the code? Not sure if you intend for others to re-use or modify your work.

Will think about it. Any suggestions?

[hafriedlander]

Hi. I'd like to use this code and your weights for gyre.ai, but also would need an open source license. Ideally MIT or Apache-2.0 if you would be willing. Thanks.