Support for React 17

The package wouldn't install on projects with react 17
```
npm ERR! code ERESOLVE
npm ERR! ERESOLVE unable to resolve dependency tree
npm ERR! 
npm ERR! While resolving: comfort-transfers@1.0.0
npm ERR! Found: react@17.0.2
npm ERR! node_modules/react
npm ERR!   react@"^17.0.1" from the root project
npm ERR!   peer react@"^16.9.0 || ^17.0.0" from gatsby@4.4.0
```