fixed markdown style errors

CppCoreGuidelines.md

@@ -6815,6 +6815,7 @@ Union rule summary:
 
 ##### Example
 
+
     ???
 
 ##### Enforcement
@@ -6825,6 +6826,7 @@ Union rule summary:
 
 ##### Reason
 
+
 Naked unions are a source of type errors.
 
 **Alternative**: Wrap them in a class together with a type field.
@@ -6835,6 +6837,8 @@ Naked unions are a source of type errors.
 
     ???
 
+
+
 ##### Enforcement
 
 ???
@@ -10322,7 +10326,7 @@ Not all data races are as easy to spot as this one.
     }
 
 Now, a compiler that does not know that `val` can change will  most likely implement that `switch` using a jump table with five entries.
-Then, a `val` outside the [0..4] range will cause a jump to an address that could be anywhere in the program, and execution would proceed there.
+Then, a `val` outside the `[0..4]` range will cause a jump to an address that could be anywhere in the program, and execution would proceed there.
 Really, "all bets are off" if you get a data race.
 Actually, it can be worse still: by looking at the generated code you may be able to determine where the stray jump will go for a given value;
 this can be a security risk.
@@ -10791,7 +10795,7 @@ A `thread` that has not been `detach()`ed when it is destroyed terminates the pr
 
     int main()
     {
-        std::thread t1{f};    // f() executes in separate thread
+        std::thread t1{f};      // f() executes in separate thread
         std::thread t2{F()};    // F()() executes in separate thread
     }  // spot the bugs
 
@@ -10805,7 +10809,7 @@ A `thread` that has not been `detach()`ed when it is destroyed terminates the pr
 
     int main()
     {
-        std::thread t1{f};    // f() executes in separate thread
+        std::thread t1{f};      // f() executes in separate thread
         std::thread t2{F()};    // F()() executes in separate thread
 
         t1.join();