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/story/Cargo.toml

@@ -0,0 +1,10 @@
+[package]
+name = "story"
+version = "0.1.0"
+edition = "2021"
+publish = false
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+gpui = { package = "gpui2", path = "../gpui2" }