message: Document opt-level 's' and 'z' stabilized in 1.28.
diff: @@ -303,6 +303,7 @@ along with the defaults for each profile.
  [profile.dev]
  opt-level = 0 # controls the `--opt-level` the compiler builds with.
  # 0-1 is good for debugging. 2 is well-optimized. Max is 3.
  + # 's' attempts to reduce size, 'z' reduces size even more.
  debug = true # include debug information (debug symbols). Equivalent to
  # `-C debuginfo=2` compiler flag.
  rpath = false # controls whether compiler should set loader paths.
  