This wants to be a small PR to improve the usability of the library, based on this conversation: https://twitter.com/grifotv/status/1127847192067215360.
Since the release of RNS there has been a new major player in the React game: hooks. And sadly `useScreens` recalls too closely Hooks, and this can lead to misunderstanding.
Changing it to `enableScreens` will make the difference clear, but at the same time it will be a BREAKING CHANGE for everyone using the lib.
So if we prefer to keep it around as useScreens I'm ok with it too, and we can close this.
Also, I did some tweaks to the README + fix some typos.
