tracing 0.1.33

This release adds new span_enabled! and event_enabled! variants of the
enabled! macro, for testing whether a subscriber would specifically enable a
span or an event.

Added

• span_enabled! and event_enabled! macros (#1900)
• Several documentation improvements (#2010, #2012)

Fixed

• Compilation warning when compiling for <=32-bit targets (including wasm32)
  (#2060)

Thanks to @guswynn, @arifd, @hrxi, @CAD97, and @name1e5s for contributing to
this release!