docs: Shift example code from README to lib.rs

We now pull from an example
- We verify it builds (wasn't doing that with README)
- We show the output for the actual code (couldn't do that from a
  rustdoc code fence)

Author: epage

README.md

@@ -3,73 +3,14 @@
 `annotate-snippets` is a Rust library for annotation of programming code slices.
 
 [![crates.io](https://img.shields.io/crates/v/annotate-snippets.svg)](https://crates.io/crates/annotate-snippets)
+[![documentation](https://img.shields.io/badge/docs-master-blue.svg)][Documentation]
 ![build status](https://github.com/rust-lang/annotate-snippets-rs/actions/workflows/ci.yml/badge.svg)
 
 The library helps visualize meta information annotating source code slices.
 It takes a data structure called `Snippet` on the input and produces a `String`
 which may look like this:
 
-```text
-error[E0308]: mismatched types
-  --> src/format.rs:52:1
-   |
-51 |   ) -> Option<String> {
-   |        -------------- expected `Option<String>` because of return type
-52 | /     for ann in annotations {
-53 | |         match (ann.range.0, ann.range.1) {
-54 | |             (None, None) => continue,
-55 | |             (Some(start), Some(end)) if start > end_index => continue,
-...  |
-71 | |         }
-72 | |     }
-   | |_____^ expected enum `std::option::Option`, found ()
-```
-
-[Documentation][]
-
-[Documentation]: https://docs.rs/annotate-snippets/
-
-Usage
------
-
-```rust
-use annotate_snippets::{Annotation, AnnotationType, Renderer, Slice, Snippet, SourceAnnotation};
-
-fn main() {
-    let snippet = Snippet {
-        title: Some(Annotation {
-            label: Some("expected type, found `22`"),
-            id: None,
-            annotation_type: AnnotationType::Error,
-        }),
-        footer: vec![],
-        slices: vec![Slice {
-            source: r#"                annotations: vec![SourceAnnotation {
-                label: "expected struct `annotate_snippets::snippet::Slice`, found reference"
-                    ,
-                range: <22, 25>,"#,
-            line_start: 26,
-            origin: Some("examples/footer.rs"),
-            fold: true,
-            annotations: vec![
-                SourceAnnotation {
-                    label: "",
-                    annotation_type: AnnotationType::Error,
-                    range: (193, 195),
-                },
-                SourceAnnotation {
-                    label: "while parsing this struct",
-                    annotation_type: AnnotationType::Info,
-                    range: (34, 50),
-                },
-            ],
-        }],
-    };
-
-    let renderer = Renderer::plain();
-    println!("{}", renderer.render(snippet));
-}
-```
+![Screenshot](./examples/expected_type.svg)
 
 Local Development
 -----------------
@@ -80,3 +21,5 @@ Local Development
 When submitting a PR please use  [`cargo fmt`][] (nightly).
 
 [`cargo fmt`]: https://github.com/rust-lang/rustfmt
+
+[Documentation]: https://docs.rs/annotate-snippets/

src/lib.rs

@@ -7,22 +7,12 @@
 //!
 //! # Example
 //!
-//! ```text
-//! error[E0308]: mismatched types
-//!   --> src/format.rs:52:1
-//!    |
-//! 51 |   ) -> Option<String> {
-//!    |        -------------- expected `Option<String>` because of return type
-//! 52 | /     for ann in annotations {
-//! 53 | |         match (ann.range.0, ann.range.1) {
-//! 54 | |             (None, None) => continue,
-//! 55 | |             (Some(start), Some(end)) if start > end_index => continue,
-//! ...  |
-//! 71 | |         }
-//! 72 | |     }
-//!    | |_____^ expected enum `std::option::Option`, found ()
+//! ```rust
+#![doc = include_str!("../examples/expected_type.rs")]
 //! ```
 //!
+#![doc = include_str!("../examples/expected_type.svg")]
+//!
 //! The crate uses a three stage process with two conversions between states:
 //!
 //! ```text