Fixing trim() explanation

Author: ThomasLandauer

components/string.rst

@@ -298,7 +298,7 @@ Methods to Pad and Trim
     // repeats the given string the number of times passed as argument
     u('_.')->repeat(10); // '_._._._._._._._._._.'
 
-    // removes the given characters (whitespace characters by default) from the string
+    // removes the given characters (default: whitespace characters) from the beginning and end of a string
     u('   Lorem Ipsum   ')->trim(); // 'Lorem Ipsum'
     u('Lorem Ipsum   ')->trim('m'); // 'Lorem Ipsum   '
     u('Lorem Ipsum')->trim('m');    // 'Lorem Ipsu'