Update readme.md

Author: dpcdpc11

Simplify Darkish/readme.md

@@ -12,7 +12,7 @@
 - now go to your profile folder. You can do it like this: load about:support in your Firefox addressbar and click on the "Open Folder" button next to "Profile Folder" label.
 - if no "chrome" folder exists there, please create one.
 - now copy the included userChrome.css and userContent.css files to that "chrome" folder.
-- make sure you use the Default Firefox theme.
+- make sure you use the Default Firefox theme and the Compact Density in the Customize settings for best results. To enable the Compact Density option, go to about:config and toggle browser.compactmode.show value to true.
 - restart Firefox and enjoy!
 
 # Credits