C++20: [[{,un}likely]]: fix the position of attributes in example (#97)

CPP20.md

@@ -265,15 +265,32 @@ for (auto v = std::vector{1, 2, 3}; auto& e : v) {
 ```
 
 ### likely and unlikely attributes
-Provides a hint to the optimizer that the labelled statement is likely/unlikely to have its body executed.
+Provides a hint to the optimizer that the labelled statement has a high probability of being executed.
+```c++
+switch (n) {
+case 1:
+  // ...
+  break;
+
+[[likely]] case 2:  // n == 2 is considered to be arbitrarily more
+  // ...            // likely than any other value of n
+  break;
+}
+```
+
+If one of the likely/unlikely attributes appears after the right parenthesis of an if-statement,
+it indicates that the branch is likely/unlikely to have its substatement (body) executed.
 ```c++
 int random = get_random_number_between_x_and_y(0, 3);
-[[likely]] if (random > 0) {
+if (random > 0) [[likely]] {
   // body of if statement
   // ...
 }
+```
 
-[[unlikely]] while (unlikely_truthy_condition) {
+It can also be applied to the substatement (body) of an iteration statement.
+```c++
+while (unlikely_truthy_condition) [[unlikely]] {
   // body of while statement
   // ...
 }