Add syntaxes and themes method

examples/advanced.rs

@@ -1,5 +1,5 @@
 /// A program that prints its own source code using the bat library
-use bat::{LineRange, PrettyPrinter, WrappingMode, PagingMode};
+use bat::{LineRange, PagingMode, PrettyPrinter, WrappingMode};
 
 fn main() {
     PrettyPrinter::new()

examples/list_syntaxes_and_themes.rs

@@ -0,0 +1,18 @@
+/// A simple program that prints its own source code using the bat library
+use bat::PrettyPrinter;
+
+fn main() {
+    let printer = PrettyPrinter::new();
+
+    println!("Syntaxes:");
+    for syntax in printer.syntaxes() {
+        println!("- {} ({})", syntax.name, syntax.file_extensions.join(", "));
+    }
+
+    println!();
+
+    println!("Themes:");
+    for theme in printer.themes() {
+        println!("- {}", theme);
+    }
+}