Update Blend Modes with example

Add a blend mode example to highlight blend mode differences between different android versions.

Bugfix for exit state with trigger condition.

Bugfix for an issue using exit states on oneshot animations with additional conditions.

Bugfix for sdk 29

Fix a bad memory access issue

Update State Machine Change callback

• removing AnimationState: from the state name on callback

Update State Machine Change callback

this now includes state Machine Name & state Name

lowering SDK requirements to 21

Merge pull request #120 from rive-app/lowerVersionRequirementsTo21

add changed needed to lower sdk to 21

Added Http to Constructor

Build simplifies getting started by allowing using urls to load network resources

State Machine - Blend State Fixes

Fixes an issue where states in state machines without animations, or with illegal setups crash the state machine
Fixes an issue where transitions out of blend states without conditions have their exit time ignored.

Added support for blend states

Adding support for blend states to rive-android!

Adding state change events & fixing some complex clipping

New somewhat more streamlined aar building, fingers crossed it works from master now