libobs: UI: Add Area scaling for downscale output

Now that Lanczos downscale blurring has been removed, the Area shader
can attempt to fill the void.

UI/window-basic-main.cpp

@@ -3447,6 +3447,8 @@ static inline enum obs_scale_type GetScaleType(ConfigFile &basicConfig)
 		return OBS_SCALE_BILINEAR;
 	else if (astrcmpi(scaleTypeStr, "lanczos") == 0)
 		return OBS_SCALE_LANCZOS;
+	else if (astrcmpi(scaleTypeStr, "area") == 0)
+		return OBS_SCALE_AREA;
 	else
 		return OBS_SCALE_BICUBIC;
 }