#29 update doc with an example of runnable rust code

book-example/src/SUMMARY.md

@@ -13,6 +13,7 @@
         - [index.hbs](format/theme/index-hbs.md)
         - [Syntax highlighting](format/theme/syntax-highlighting.md)
     - [MathJax Support](format/mathjax.md)
+    - [Rust code specific features](format/rust.md)
 - [Rust Library](lib/lib.md)
 -----------
 [Contributors](misc/contributors.md)

book-example/src/format/example.rs

@@ -0,0 +1,6 @@
+fn main() {
+    println!("Hello World!");
+#
+#    // You can even hide lines! :D
+#   println!("I am hidden! Expand the code snippet to see me");
+}

book-example/src/format/rust.md

@@ -0,0 +1,42 @@
+# Rust code specific features
+
+## Hiding code lines
+
+There is a feature in mdBook that let's you hide code lines by prepending them with a `#`.
+
+```bash
+#fn main() {
+    let x = 5;
+    let y = 6;
+
+    println!("{}", x + y);
+#}
+```
+
+Will render as
+
+```rust
+#fn main() {
+    let x = 5;
+    let y = 7;
+
+    println!("{}", x + y);
+#}
+```
+
+
+## Inserting runnable Rust files
+
+With the following syntax, you can insert runnable Rust files into your book:
+
+```hbs
+\{{#playpen file.rs}}
+```
+
+The path to the Rust file has to be relative from the current source file.
+
+When play is clicked, the code snippet will be send to the [Rust Playpen]() to be compiled and run. The result is send back and displayed directly underneath the code.
+
+Here is what a rendered code snippet looks like:
+
+{{#playpen example.rs}}