feat(new converter): boolean

Author: jyounce

README.md

@@ -128,6 +128,7 @@ All methods convert the attribute's value to a type and returns it.
 The first param is the attribute's value which is always a string.
 
 * Methods
+	* boolean(val) :boolean
 	* valueless(val) :boolean
 
 ```js

src/client/scripts/public/props/converters.js

@@ -8,6 +8,9 @@
  - The first param is the attr val which is always a string.
  *************************************************************/
 const Converters = {
+	boolean(val) { // :boolean
+		return /^true$/i.test(val);
+	},
 	valueless(val) { // :boolean
 		val = val.trim();
 		if (!val) return true; // valueless attr is empty string