nvidia/cv: Publicly inherit from std::runtime_error

It wasn't possible to cast these exceptions to the underlying type, so they were treated as unknown exceptions.

source/nvidia/cv/nvidia-cv.hpp

@@ -288,7 +288,7 @@ namespace streamfx::nvidia::cv {
 		static std::shared_ptr<::streamfx::nvidia::cv::cv> get();
 	};
 
-	class exception : std::runtime_error {
+	class exception : public std::runtime_error {
 		result _code;
 
 		public: