#38 Added shadow attribute for Style

Author: malcommac

README.md

@@ -487,6 +487,7 @@ The following properties are available:
 | font                          | `FontConvertible`                       | font used in text                                                                                                                          | 
 | color                         | `ColorConvertible`                      | foreground color of the text                                                                                                               | 
 | backColor                     | `ColorConvertible`                      | background color of the text                                                                                                               | 
+| shadow                     | `NSShadow`                      | shadow effect of the text                                                                                                             | 
 | underline                     | `(NSUnderlineStyle?,ColorConvertible?)` | underline style and color (if color is nil foreground is used)                                                                             | 
 | strikethrough                 | `(NSUnderlineStyle?,ColorConvertible?)` | strikethrough style and color (if color is nil foreground is used)                                                                         | 
 | baselineOffset                | `Float`                                 | character’s offset from the baseline, in point                                                                                             | 

Sources/SwiftRichString/Style/Style.swift

@@ -325,6 +325,20 @@ public class Style: StyleProtocol {
 		}
 	}
 
+	#if os(iOS) || os(tvOS) || os(macOS)
+
+	/// The value of this attribute is an `NSShadow` object. The default value of this property is nil.
+	public var shadow: NSShadow? {
+		set {
+			self.set(attribute: shadow, forKey: .shadow)
+		}
+		get {
+			return self.get(attributeForKey: .shadow)
+		}
+	}
+
+	#endif
+	
 	#if os(iOS) || os(tvOS) || os(watchOS)
 
 	/// Enable spoken of all punctuation in the text.