Recude quality in image variant creation

Currently, we create variant image sizes with the script available in the scripts/ directory. This works pretty fine.

I suggest to reduce the quality level, in order to further reduce the size of images that need to be loaded. I can't see a real difference, but the image size was more than halved for some examples. Something along this way:

diff --git a/scripts/create_jumbotron_variants.sh b/scripts/create_jumbotron_variants.sh
index b24b7d6..3df4855 100755
--- a/scripts/create_jumbotron_variants.sh
+++ b/scripts/create_jumbotron_variants.sh
@@ -84,12 +84,12 @@ do
             else
                 # Create new version for this breakpoint
                 echo "Generating $target_file ($target_width px)"
-                convert "$source_file" -resize "$target_width" "$target_file"
+                convert "$source_file" -resize "$target_width" -quality 50 "$target_file"
             fi
         else
-            # Instead of upscaling, create a relative link to the original
-            echo "Creating link $target_file (Source smaller then target)"
-            ln -sr "$source_file" "$target_file"
+            # Instead of upscaling, only reduce quality
+            echo "Reducing quality of $target_file"
+            convert "$source_file" -quality 50 "$target_file"
         fi
     done
 done

@hueser93 @erxleb87 What do you say?