Add Node properties for previous and next sibling elements

HTMLKit/HTMLNode.h

@@ -62,6 +62,10 @@ typedef NS_ENUM(unsigned short, HTMLDocumentPosition)
 
 @property (nonatomic, strong, readonly) HTMLNode *nextSibling;
 
+@property (nonatomic, strong, readonly) HTMLElement *previousSiblingElement;
+
+@property (nonatomic, strong, readonly) HTMLElement *nextSiblingElement;
+
 @property (nonatomic, copy) NSString *textContent;
 
 @property (nonatomic, strong, readonly)	NSString *outerHTML;

HTMLKit/HTMLNode.m

@@ -99,6 +99,24 @@
 	return [_parentNode childNodeAtIndex:index + 1];
 }
 
+- (HTMLElement *)previousSiblingElement
+{
+	HTMLNode *node = self.previousSibling;
+	while (node && node.nodeType != HTMLNodeElement) {
+		node = node.previousSibling;
+	}
+	return node.asElement;
+}
+
+- (HTMLElement *)nextSiblingElement
+{
+	HTMLNode *node = self.previousSibling;
+	while (node && node.nodeType != HTMLNodeElement) {
+		node = node.nextSibling;
+	}
+	return node.asElement;
+}
+
 - (NSString *)textContent
 {
 	return nil;