Used date timestamp for screenshot name

src/FractalApp.cpp

@@ -680,7 +680,13 @@ void FractalInspectorApp::TakeScreenshot() {
     }
     uint8_t* frameBuffer = reinterpret_cast<uint8_t*>(pdatac3.data());
 
-    std::ofstream file("screenshot.bmp", std::ios::out | std::ios::binary);
+    time_t t = std::time(nullptr);
+    tm tm = *std::localtime(&t);
+
+    std::ostringstream filename;
+    filename << std::put_time(&tm, "%Y-%m-%d %H-%M-%S") << ".bmp";
+
+    std::ofstream file(filename.str(), std::ios::out | std::ios::binary);
 
     Vector2i wh = this->canvas->GetDimensions();