message: Add `#[non_exhaustive]` to example actionable error in RFC
diff: @@ -233,6 +233,8 @@ Actionable errors are represented as enums. If an error variant has an error sou
  information, it must use a separate context struct that is referenced via tuple in the enum. For example:
  ```rust
  +// Good: new error types can be added in the future
  +#[non_exhaustive]
  pub enum Error {
  // Good: This is exhaustive and uses a tuple, but its sole member is an extensible struct with private fields
  VariantA(VariantA),
  