Support React 17

[avivace]

We're using React-SearchKit which depends on react-overridable, which needs React <= 16.

Our app runs okay on React 17 forcefully installing react-overridable with npm install --force. I also tried to upgrade react-overridable to require React 17 ("react": "^17.0.2") and run npm run test with positive results.

Is there something else I can check to be sure we can upgrade?

[ThiefMaster]

PR welcome :) We use react 17 in indico so no changes needed

[avivace]

Great, I opened #14