fix: add ansi_buffer example

Cargo.toml

@@ -182,8 +182,8 @@ harness = false
 
 
 [[example]]
-name = "barchart"
-required-features = ["crossterm"]
+name = "ansi_buffer"
+required-features = ["unstable-widget-ext", "unstable-widget-ref"]
 doc-scrape-examples = true
 
 [[example]]

examples/ansi_buffer.rs

@@ -0,0 +1,8 @@
+use ratatui::{prelude::*, widgets::ansi_string_buffer::AnsiStringBuffer};
+
+fn main() {
+    let mut buf = AnsiStringBuffer::new(5, 2);
+    buf.render_ref(&Line::styled("Hello", Color::Blue), Rect::new(0, 0, 5, 1));
+    buf.render_ref(&Line::styled("World", Color::Green), Rect::new(0, 1, 5, 1));
+    println!("{buf}");
+}