Choose a more interesting example snippet (#1394)

playground/src/App.tsx

@@ -8,7 +8,32 @@ import { AVAILABLE_OPTIONS } from "./ruff_options";
 import { Config, getDefaultConfig, toRuffConfig } from "./config";
 import { Options } from "./Options";
 
-const DEFAULT_SOURCE = "print(1 + 2)";
+const DEFAULT_SOURCE =
+  "# Define a function that takes an integer n and returns the nth number in the Fibonacci\n" +
+  "# sequence.\n" +
+  "def fibonacci(n):\n" +
+  "  if n == 0:\n" +
+  "    return 0\n" +
+  "  elif n == 1:\n" +
+  "    return 1\n" +
+  "  else:\n" +
+  "    return fibonacci(n-1) + fibonacci(n-2)\n" +
+  "\n" +
+  "# Use a for loop to generate and print the first 10 numbers in the Fibonacci sequence.\n" +
+  "for i in range(10):\n" +
+  "  print(fibonacci(i))\n" +
+  "\n" +
+  "# Output:\n" +
+  "# 0\n" +
+  "# 1\n" +
+  "# 1\n" +
+  "# 2\n" +
+  "# 3\n" +
+  "# 5\n" +
+  "# 8\n" +
+  "# 13\n" +
+  "# 21\n" +
+  "# 34\n";
 
 function restoreConfigAndSource(): [Config, string] {
   const value = lzstring.decompressFromEncodedURIComponent(