Add `license` key to package.json.
Add `license` key to package.json.

We’re already using MIT, but now it’s in the package.json to make NPM (and you!) happy.

dapriett/connect-assets,codynguyen/connect-assets,adunkman/connect-assets,codynguyen/connect-assets,inukshuk/connect-assets,nmalacarne/connect-assets,luckycadow/connect-assets,adunkman/connect-assets