crates: vendor annotate-snippets crate

This merely adds the crate to our repository. Some cosmetic changes are
made to make it work in our repo and follow our conventions, such as
changing the name to `ruff_annotate_snippets`. We retain the original
license information. We do drop some things, such as benchmarks, but
keep tests and examples.

crates/ruff_annotate_snippets/examples/footer.rs

@@ -0,0 +1,22 @@
+use ruff_annotate_snippets::{Level, Renderer, Snippet};
+
+fn main() {
+    let message =
+        Level::Error
+            .title("mismatched types")
+            .id("E0308")
+            .snippet(
+                Snippet::source("        slices: vec![\"A\",")
+                    .line_start(13)
+                    .origin("src/multislice.rs")
+                    .annotation(Level::Error.span(21..24).label(
+                        "expected struct `annotate_snippets::snippet::Slice`, found reference",
+                    )),
+            )
+            .footer(Level::Note.title(
+                "expected type: `snippet::Annotation`\n   found type: `__&__snippet::Annotation`",
+            ));
+
+    let renderer = Renderer::styled();
+    anstream::println!("{}", renderer.render(message));
+}