v1.4.0

• [2cbecba, 4611fa8] don't register event handlers multiple times in case more than one ViewportProvider is already rendered within the same tree. This is mostly interesting for libraries that are rendering their own Provider component which implements the ViewportProvider #3
• [b2d3fef] add a helpful warning in development in case a ObserveViewport component is rendered without a ViewportProvider as its parent