LICENSE.md file is missing (but listed as MIT in package.json)

[jamiecopeland]

First off thank you! This package has made so many things easer, especially dealing with dates over long ranges that involve DST shifts 🥰.

The package.json has the license down as MIT, but the LICENSE.md file seems to be missing from the repo.

Lots of companies have strict rules around package usage and this may be a blocker in some cases.

I can create a PR with the same MIT LICENSE.md from the main date-fns library if that's any help?