v0.19.0

Swift

• Update to build with Swift 5.
• Allow sinks to be reused across render passes if a sink of the same action type is declared. (#443)
• Support updating the root workflow input on a WorkflowHost. (#351)
• Add support for RenderTester to expect child workflows and outputs. (#442)

Kotlin

• WorkflowRunner now delivers single result instead of output stream (#468)
• Use single object for noAction instead of creating it on every call (#473)
• Upgrade AGP to 3.5.0-rc01. (#484)
• Use Java 8 (#492)