Respect Network Information API in browser variant of cordova-plugin-network-information

Chrome 61+ implemented the Network Information API, but the current implementation of the cordova-plugin-network-information for browsers does not respect this API if it's available.

See https://github.com/apache/cordova-plugin-network-information/blob/master/src/browser/network.js#L25 for how it determines the connection via getConnectionInfo.

It would be a good improvements if the Network Information API is used if available.

More information:

• https://wicg.github.io/netinfo/
• https://www.chromestatus.com/feature/6338383617982464