Adding XML style guide

manual/en-US/coding-standards/chapters/xml.md

@@ -0,0 +1,57 @@
+## XML Files
+
+### Attributes
+
+* Each attribute is on its own line.
+* The four attributes `name`, `type`, `label` and `description` should be written in this order and at the top of the element definition.
+
+### Closing Elements
+
+Elements should be closed with the closing tag on a new line.
+
+### Exception
+
+When the element only has few attributes, then the whole element can stay on the same line.
+A max line length of 100 characters is recommended for good reading.
+
+#### Examples
+
+Element is **empty**:
+````
+<field
+	name="abc"
+	type="text"
+	label="Empty Field"
+	description="Empty field without options"
+	/>
+````
+
+Element is **not empty**:
+````
+<field
+	name="abc"
+	type="radio"
+	label="Field"
+	description="Field with options"
+	>
+	<option value="1">JYES</option>
+	<option value="0">JNO</option>
+</field>
+
+<field
+	name="abc"
+	type="radio"
+	label="Field"
+	description="Field with options"
+	>
+	<option
+		value="1"
+		foo="bar"
+		>
+		SOMETHING_VERY_LONG
+	</option>
+	<option value="0">
+		SOMETHING_VERY_LONG
+	</option>
+</field>
+````

manual/en-US/menu.md

@@ -5,6 +5,7 @@
     - [Inline Code Comments](coding-standards/chapters/inline-comments.md)
     - [DocBlocks](coding-standards/chapters/docblocks.md)
     - [PHP Code](coding-standards/chapters/php.md)
+    - [XML](coding-standards/chapters/xml.md)
 - **Clientside Syntax Styleguides**
     - [HTML](coding-standards/chapters/html.md)
     - [CSS](coding-standards/chapters/css.md)