Extract Story into separate story crate (#3378)

This PR extracts the `Story` component into a separate `story` crate so
that it can be shared among various crates that define stories.

Release Notes:

- N/A

---------

Co-authored-by: Nate Butler <iamnbutler@gmail.com>

crates/theme2/src/theme2.rs

@@ -144,8 +144,3 @@ pub struct DiagnosticStyle {
     pub hint: Hsla,
     pub ignored: Hsla,
 }
-
-#[cfg(feature = "stories")]
-mod story;
-#[cfg(feature = "stories")]
-pub use story::*;