main: add some docs

Author: marcoieni

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "rust-gh-example"
-version = "0.1.3"
+version = "0.1.4"
 authors = ["MarcoIeni <[email protected]>"]
 edition = "2018"
 description = "Example of Rust GitHub template"

src/main.rs

@@ -2,6 +2,7 @@ fn main() {
     println!("The answer to the ultimate question is {}", answer());
 }
 
+/// Hello from Magrathea
 fn answer() -> u32 {
     42
 }