React 17 compatibility

### **bug report**/**feature request**

### What is the current behavior?

React 17 is not listed as a peerDependency, causing NPM to throw "could not resolve dependency" when using React 17.

### What is the expected behavior?

As I believe this package is pefectly able to work under React 17, peerDependencies should be updated:

```
{
"react": "^15.3.0 || ^16.0.0-0 || ^17.0.0",
"react-dom": "^15.3.0 || ^16.0.0-0 || 17.0.0",
}
```

### What's your environment?

Final form: 4.20.1
React-final-form: 6.5.2
React-final-form-html5-validation: 1.1.0

Node 15.2.0
NPM 7.0.8