canvas.md

## canvas

<!-- UTSCOMJSON.canvas.description -->

<!-- UTSCOMJSON.canvas.compatibility -->

<!-- UTSCOMJSON.canvas.attribute -->

<!-- UTSCOMJSON.canvas.event -->

<!-- UTSCOMJSON.canvas.component_type-->

<!-- UTSCOMJSON.canvas.children -->

<!-- UTSCOMJSON.canvas.example -->

<!-- UTSCOMJSON.canvas.reference -->