Add source code documentation for the CSS Selectors parsers

HTMLKit/CSSNthExpressionParser.h

@@ -11,8 +11,19 @@
 
 NS_ASSUME_NONNULL_BEGIN
 
+/**
+ The Nth-Expression Parser.
+
+ Parses CSS nth-expressions, e.g. '-2n+3', 'odd', ...etc.
+ */
 @interface CSSNthExpressionParser : NSObject
 
+/**
+ Parses a CSS nth-exrepssion string.
+
+ @param expression The expression string to parse.
+ @see CSSNthExpression
+ */
 + (CSSNthExpression)parseExpression:(NSString *)expression;
 
 @end

HTMLKit/CSSSelectorParser.h

@@ -12,8 +12,23 @@ NS_ASSUME_NONNULL_BEGIN
 
 @class CSSSelector;
 
+/**
+ The CSS Selectors Parser.
+
+ Parses CSS Level 3 Selectors:
+ http://www.w3.org/TR/css3-selectors/
+ */
 @interface CSSSelectorParser : NSObject
 
+/**
+ Parses a CSS3 selector string.
+
+ @param string The CSS3 selector string.
+ @param error If an error occurs, upon return contains an `NSError` object that describes the problem.
+ @returns A parsed CSSSelector, `nil` if an error occurred.
+
+ @see CSSelector
+ */
 + (CSSSelector *)parseSelector:(NSString *)string error:(NSError **)error;
 
 @end