Add comments to functions (bobbyiliev#26)

Author: shmick

ebook/en/content/012-bash-functions.md

@@ -44,4 +44,23 @@ function hello(){
 hello DevDojo
 ```
 
-In the next few chapters we will be using functions a lot!
+Functions should have comments mentioning description, global variables, arguments, outputs, and returned values, if applicable
+
+```bash
+#######################################
+# Description: Hello function
+# Globals:
+#   None
+# Arguments:
+#   Single input argument
+# Outputs:
+#   Value of input argument
+# Returns:
+#   0 if successful, non-zero on error.
+#######################################
+function hello(){
+    echo "Hello $1!"
+}
+```
+
+In the next few chapters we will be using functions a lot!