Optimize image qualities and a fix (alshedivat#762)

* blog tag-list

* optimize publication preview

* better compression

* optimize jpg project images

* reduce sizes of project images

* fix

Author: rohandebsarkar

_config.yml

@@ -258,7 +258,7 @@ imagemagick:
     - ".png"
     - ".tiff"
   output_formats:
-    webp: "-quality 75%"
+    webp: "-resize 800x"
 
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