Add license

[EvanHahn]

I'd like to add a simplified version of the clock to my website but don't want to break any laws by copying some of the code.

Could we add a license? Personally, I'd vote for the permissive Unlicense, but it's up to you.

Happy to make a pull request to add this if that'd be useful.

[adrian-the-git]

@EvanHahn We're discussing the license for this and forthcoming code. I unfortunately can't provide you with more details except to say that you may use the unmodified version for now. If you'd like to strip some of the "flatten the curve" logic expect that coming shortly in the new year.