Add restProps to anchor

[clementmoine]

The user is able to provide style, onClick and className parameters for example when creating a Link from react-navigation-web.

restProps is meant to contain all props that are not already extracted from this.props that allow the user to choose wether he want to add className, onClick, style for any reason.

Use case example :

import React, { Component } from 'react'
import { Link } from '@react-navigation/web'

class example extends Component {
  render() {
    return (
      <Link
        className="my-classname"
        routeName="MyPage"
        style={{ anyStyleProperty: 'anyValue' }}
      >
        <span>Some text</span>
      </Link>
    )
  }
}

export default example

Issue #5 is solved with this PR

[ericvicenti]

What if we renamed this to anchorProps, (with no "..." spreading) so that the use is explicit. I want to make sure we can add functionality to this component in the future, without breaking people's apps. This way we don't have the same namespace as the component