[How to create a new Format] Add new page

How-to-create-a-new-Format.md

@@ -0,0 +1,24 @@
+Create a new file in the `formats/` folder (see [Folder structure](Folder-structure)).
+
+The file must be named according to following specification:
+
+* It starts with the type
+* The file name must end with 'Format'
+* The file type must be PHP, written in small letters (seriously!) ".php"
+
+**Examples:**
+
+Type | Filename
+-----|---------
+Atom | AtomFormat.php
+Html | HtmlFormat.php
+
+The file must start with the PHP tags and end with an empty line. The closing tag `?>` is [omitted](http://php.net/basic-syntax.instruction-separation).
+
+Example:
+
+```PHP
+<?PHP
+    // PHP code here
+// This line is empty (just imagine it!)
+```