feat: add min_fps_target setting (#1043)

src/config.cpp

@@ -331,6 +331,7 @@ namespace config {
     0,  // hevc_mode
     0,  // av1_mode
 
+    1,  // min_fps_factor
     2,  // min_threads
     {
       "superfast"s,  // preset
@@ -1030,6 +1031,7 @@ namespace config {
     string_f(vars, "encoder", video.encoder);
     string_f(vars, "adapter_name", video.adapter_name);
     string_f(vars, "output_name", video.output_name);
+    int_between_f(vars, "min_fps_factor", video.min_fps_factor, { 1, 3 });
 
     path_f(vars, "pkey", nvhttp.pkey);
     path_f(vars, "cert", nvhttp.cert);