Implement enum for Layout data type

gui/window/main.xml

@@ -1,4 +1,4 @@
-<!-- Called as <window:main width="1920px" height="1080px" /> -->
+<!-- Instantiated by the window and called with absolute dimensions such as: <window:main width="1920px" height="1080px" /> -->
 <window:main>
 	<col width="100%" height="100%">
 		<!-- Header -->

src/layout_abstract_types.rs

@@ -1,4 +1,5 @@
 use crate::color::Color;
+use crate::layout_abstract_syntax::*;
 
 #[derive(Debug)]
 pub struct VariableParameter {
@@ -36,7 +37,7 @@ pub enum TypeValueOrArgument {
 
 #[derive(Debug)]
 pub enum TypeName {
-	// Layout, // TODO
+	Layout,
 	Integer,
 	Decimal,
 	AbsolutePx,
@@ -53,7 +54,7 @@ pub enum TypeName {
 
 #[derive(Debug)]
 pub enum TypeValue {
-	// Layout(()), // TODO
+	Layout(Vec<rctree::Node<LayoutAbstractNode>>),
 	Integer(i64),
 	Decimal(f64),
 	AbsolutePx(f32),

src/layout_attribute_parser.rs

@@ -224,7 +224,7 @@ impl AttributeParser {
 
 								// Return the case-insensitive TypeName enum for the individual type
 								match &individual_type.to_ascii_lowercase()[..] {
-									// "layout" => TypeName::Layout, // TODO
+									"layout" => TypeName::Layout,
 									"integer" => TypeName::Integer,
 									"decimal" => TypeName::Decimal,
 									"absolutepx" => TypeName::AbsolutePx,