Allow React 17 as peer dependency (#123)

React 17 has been around for a little bit. I'm using it in a new project and would like to use this library, but the `peerDependencies` are too restrictive. The release notes suggest that there should be exceeding few breaking changes between React 16 and 17, so I believe this is a safe change: https://reactjs.org/blog/2020/10/20/react-v17.html

Author: daiyi

package.json

@@ -29,7 +29,7 @@
     "resize-observer-polyfill": "^1.5.0"
   },
   "peerDependencies": {
-    "react": "16.x"
+    "react": "16.x || 17.x"
   },
   "devDependencies": {
     "all-contributors-cli": "^6.15.0",