message: Fix small format bug in tracing documentation
  * Fix small format bug in tracing documentation
  Typo on the docs index page which prevents link rendering
  * Fix another dead link in documentation (span)
diff: //! ### Shorthand Macros
  //!
  //! `tracing` also offers a number of macros with preset verbosity levels.
  -//! The [`trace!`], [`debug!`], [`info!`], [`warn!]`, and [`error!`] behave
  +//! The [`trace!`], [`debug!`], [`info!`], [`warn!`], and [`error!`] behave
  //! similarly to the [`event!`] macro, but with the [`Level`] argument already
  //! specified, while the corresponding [`trace_span!`], [`debug_span!`],
  //! [`info_span!`], [`warn_span!`], and [`error_span!`] macros are the same,
  -//! but for the `[span!`] macro.
  +//! but for the [`span!`] macro.
  //!
  //! These are intended both as a shorthand, and for compatibility with the [`log`]
  //! crate (see the next section).
  