Update dependency constraints

[phlipper]

Overview

This PR updates the dependency constraints to make updates more flexible for library users.

Move react and react-dom to peerDependencies:

peerDependencies specifies which versions your reusable component supports/requires.

Putting react in dependencies can cause multiple versions of React to be installed if somebody uses your component but has a different version of React in their own package.json.

Move react-scripts to devDependencies:

The react-scripts package contains development tools and dependencies which are not required by the library consumer and can cause version conflicts.

Notes

• Several of the devDepenencies have been updated via npm audit fix due to active vulnerabilities
• The unused enzyme-adapter-react-15 has been removed
• jest (which is included via react-scripts) has been replaced with jest-cli - yarn test would properly run tests but npm test would not

[caaatisgood]

oh wow, learned a lot from the description! thanks @phlipper!

[alexgarces]

This is awesome @phlipper, I also learned a lot! I added the PR to the next version. Thanks a lot!