fix: upgrade minimum React version to 16.8

Author: FezVrasta

package.json

@@ -59,13 +59,11 @@
   ],
   "peerDependencies": {
     "@popperjs/core": "^2.0.0",
-    "react": "0.14.x || ^15.0.0 || ^16.0.0"
+    "react": "^16.8.0"
   },
   "dependencies": {
     "@babel/runtime": "^7.9.2",
-    "create-react-context": "^0.3.0",
     "deep-equal": "^2.0.1",
-    "prop-types": "^15.6.1",
     "warning": "^4.0.2"
   },
   "devDependencies": {

src/Manager.js

@@ -1,11 +1,10 @@
 // @flow
 import * as React from 'react';
-import createContext, { type Context } from 'create-react-context';
 
-export const ManagerReferenceNodeContext: Context<?HTMLElement> = createContext();
-export const ManagerReferenceNodeSetterContext: Context<
+export const ManagerReferenceNodeContext = React.createContext<?HTMLElement>();
+export const ManagerReferenceNodeSetterContext = React.createContext<
   void | ((?HTMLElement) => void)
-> = createContext();
+>();
 
 export type ManagerProps = {
   children: React.Node,