Add leading example sentence for warning references in range [C4271, C4310]

Author: Rageking8

docs/error-messages/compiler-warnings/compiler-warning-level-1-c4286.md

@@ -15,6 +15,8 @@ The specified exception type is handled by a previous handler. The type for the
 
 ## Example
 
+The following example generates C4286:
+
 ```cpp
 //C4286.cpp
 // compile with: /W1

docs/error-messages/compiler-warnings/compiler-warning-level-2-c4275.md

@@ -31,6 +31,8 @@ C4275 can be ignored in Visual C++ if you are deriving from a type in the C++ St
 
 ## Example
 
+The following example generates C4275:
+
 ```cpp
 // C4275.cpp
 // compile with: /EHsc /MTd /W2 /c

docs/error-messages/compiler-warnings/compiler-warning-level-2-c4308.md

@@ -17,6 +17,8 @@ The [`/sdl` (Enable Additional Security Checks)](../../build/reference/sdl-enabl
 
 ## Example
 
+The following example generates C4308:
+
 ```cpp
 // C4308.cpp
 // compile with: /W2