message: Add word of caution about `Float` and `no_std`
diff: @@ -10,7 +10,11 @@ use {ToPrimitive, Num, NumCast};
  // FIXME: these doctests aren't actually helpful, because they're using and
  // testing the inherent methods directly, not going through `Float`.
  -/// Floating point operations that work with `std`.
  +/// Floating point operations.
  +///
  +/// Please note that some methods are disabled for `no_std`. If you implement it
  +/// only for `no_std`, the build will fail if anyone else in the dependency
  +/// graph enables `num-traits/std`.
  pub trait Float
  : Num
  + Copy
  