subscriber: prepare to release 0.2.19

[hawkw]

0.2.19 (June 25, 2021)

Deprecated

• registry: SpanRef::parents, SpanRef::from_root, and
  Context::scope iterators, which are replaced by new SpanRef::scope
  and Scope::from_root iterators (core: add as_str() for Level #1413)

Added

• registry: SpanRef::scope method, which returns a leaf-to-root
  Iterator including the leaf span (core: add as_str() for Level #1413)
• registry: Scope::from_root method, which reverses the scope
  iterator to iterate root-to-leaf (core: add as_str() for Level #1413)
• registry: Context::event_span method, which looks up the parent
  span of an event (Add Context method for resolving an Event's SpanRef #1434)
• registry: Context::event_scope method, returning a Scope
  iterator over the span scope of an event (Add Context method for resolving an Event's SpanRef #1434)
• fmt: MakeWriter::make_writer_for method, which allows returning
  a different writer based on a span or event's metadata (subscriber: add MakeWriter::make_writer_for #1141)
• fmt: MakeWriterExt trait, with with_max_level,
  with_min_level, with_filter, and, and or_else combinators
  (subscriber: add MakeWriter combinators #1274)
• fmt: MakeWriter implementation for Arc<W> where &W: io::Write
  (subscriber: add MakeWriter combinators #1274)

Thanks to @teozkr and @Folyd for contributing to this release!