Modify rule S6228: reword and add documentation link

rules/S6228/cfamily/rule.adoc

@@ -1,20 +1,20 @@
 == Why is this an issue?
 
-Since integers are usually represented in binary form in computers, it is efficient to check if a given number is a power of two by checking if its  ``++unsigned++`` representation has a single bit set.
+Since integers are usually represented in binary form in computers, it is efficient to check if a given number is a power of two by checking if its  ``++unsigned++`` representation has a single-bit set.
 
 
-In {cpp} such check could be expressed as ``++x & (x-1) == 0++``. However, the intent of this expression is unclear. Furthermore, it requires to take special care for the value ``++0++``, which would pass the above check, while not having any bit set and not being a power of two.
+In {cpp} such check could be expressed as ``++x & (x-1) == 0++``. However, the intent of this expression is unclear. Furthermore, it requires special care for the value ``++0++``, which would pass the above check without having any bit set or being a power of two.
 
 
-This check can be expressed more clearly with the ``++std::has_single_bit++`` function template, introduced in {cpp}20.
+The ``++std::has_single_bit++`` function template, introduced in {cpp}20 that checks if an integer is a power of two, expresses the intent more clearly.
 
 
-This rule reports computations that could be replaced with ``++std::has_single_bit++`` .
+This rule reports computations that could be replaced with ``++std::has_single_bit++``.
 
 
 === Noncompliant code example
 
-[source,cpp]
+[source,cpp,diff-id=1,diff-type=noncompliant]
 ----
 void f(unsigned x) {
   if ((x > 0) && !(x & (x-1))) { // Noncompliant
@@ -27,7 +27,7 @@ void f(unsigned x) {
 
 === Compliant solution
 
-[source,cpp]
+[source,cpp,diff-id=1,diff-type=compliant]
 ----
 void f(unsigned x) {
   if (std::has_single_bit(x)) {
@@ -37,4 +37,6 @@ void f(unsigned x) {
 }
 ----
 
+== Resources
 
+* {cpp} reference - https://en.cppreference.com/w/cpp/numeric/has_single_bit[std::has_single_bit]