Add example to README.

README.md

@@ -71,6 +71,47 @@ For those who actually want their own language
 * Extend the language with [custom syntax](https://rhai.rs/book/engine/custom-syntax.html).
 
 
+Example
+-------
+
+The [`scripts`](https://github.com/rhaiscript/rhai/tree/master/scripts) subdirectory contains sample Rhai scripts.
+
+Below is a the standard _Fibonacci_ example for scripting languages:
+
+```js
+// This Rhai script calculates the n-th Fibonacci number using a really dumb algorithm
+// to test the speed of the scripting engine.
+
+const TARGET = 28;
+const REPEAT = 5;
+
+fn fib(n) {
+    if n < 2 {
+        n
+    } else {
+        fib(n-1) + fib(n-2)
+    }
+}
+
+print(`Running Fibonacci(28) x ${REPEAT} times...`);
+print("Ready... Go!");
+
+let result;
+let now = timestamp();
+
+for n in range(0, REPEAT) {
+    result = fib(TARGET);
+}
+
+print(`Finished. Run time = ${now.elapsed} seconds.`);
+
+print(`Fibonacci number #${TARGET} = ${result}`);
+
+if result != 317_811 {
+    print("The answer is WRONG! Should be 317,811!");
+}
+```
+
 Project Site
 ------------