v0.3.0

This is the first release of this library published to Maven Central.

• Introduce inspection mode for peering into the past. (#12)
• Add RTL support to the Slide transition.
• Add system back support to the viewer app. (#14)
• Replace custom opacity modifier with the new built-in one.
• Add more API documentation to the README.
• Tweak the sample custom transition. (#10)