feat(userspace): Add comments to explain "banned.h".

Fixes #1035

Signed-off-by: Vaibhav <vrongmeal@gmail.com>

userspace/engine/json_evt.cpp

@@ -21,7 +21,7 @@ limitations under the License.
 
 #include "falco_common.h"
 #include "json_evt.h"
-#include "banned.h"
+#include "banned.h" // This raises a compilation error when certain functions are used
 
 using json = nlohmann::json;
 using namespace std;