assetUriMatcher function
Implementation
CustomRenderMatcher assetUriMatcher() => (context) =>
context.tree.element?.attributes.cast() != null &&
_src(context.tree.element!.attributes.cast()) != null &&
_src(context.tree.element!.attributes.cast())!.startsWith("asset:") &&
!_src(context.tree.element!.attributes.cast())!.endsWith(".svg");