Add compatibility with React 17 and npm 7

[fzaninotto]

React 17 was published in october 2020 (https://github.com/facebook/react/blob/master/CHANGELOG.md#1700-october-20-2020).

npm 7 was published in october 2020 (https://github.blog/2020-10-13-presenting-v7-0-0-of-the-npm-cli/) and is bundled by default with node 15.

npm 7 changes the way peer dependencies are handled. As a consequence, connected-react-router doesn't work with react 17, because the peerDependency on React is on ^16.4.0. As a consequence, all packages depending on connected-react-router and React 17 cannot be installed with npm 7 (e.g. marmelab/react-admin#5908)

I know this is not your repo's fault, and that npm shouldn't have broken BC, but the simple change I propose is an easy fix. So please consider merging it and releasing a new version.

Thanks in advance!

[supasate]

It's duplicate with #460, but thanks @fzaninotto anyway. I really appreciate the detailed you provided.

[dewrox]

@supasate, Actually #460 is not whole.

The following is missing

Line 71 "react": "^16.4.0 || ^17.0.0",
Line 72 "react-dom": "^16.4.0 || ^17.0.0",