Add leading example sentence for warning references in range [C4121, C4160]

Author: Rageking8

docs/error-messages/compiler-warnings/compiler-warning-level-1-c4138.md

@@ -15,6 +15,8 @@ The closing-comment delimiter is not preceded by an opening-comment delimiter. T
 
 ## Example
 
+The following example generates C4138:
+
 ```cpp
 // C4138a.cpp
 // compile with: /W1

docs/error-messages/compiler-warnings/compiler-warning-level-1-c4141.md

@@ -11,6 +11,8 @@ helpviewer_keywords: ["C4141"]
 
 ## Example
 
+The following example generates C4141:
+
 ```cpp
 // C4141.cpp
 // compile with: /W1 /LD

docs/error-messages/compiler-warnings/compiler-warning-level-1-c4154.md

@@ -15,6 +15,8 @@ You cannot use **`delete`** on an array, so the compiler converts the array to a
 
 ## Example
 
+The following example generates C4154:
+
 ```cpp
 // C4154.cpp
 // compile with: /c /W1

docs/error-messages/compiler-warnings/compiler-warning-level-2-c4156.md

@@ -17,6 +17,8 @@ This warning occurs only under Microsoft extensions (/Ze).
 
 ## Example
 
+The following example generates C4156:
+
 ```cpp
 // C4156.cpp
 // compile with: /W2

docs/error-messages/compiler-warnings/compiler-warning-level-4-c4125.md

@@ -15,6 +15,8 @@ The compiler evaluates the octal number without the decimal digit and assumes th
 
 ## Example
 
+The following example generates C4125:
+
 ```cpp
 // C4125a.cpp
 // compile with: /W4