Add experiments

user.js

 user_pref("media.eme.enabled", true); // allow DRM
 user_pref("toolkit.legacyUserProfileCustomizations.stylesheets", true); // enable user styles
 user_pref("layout.css.has-selector.enabled", true); // enable :has filter
+user_pref("layout.css.grid-template-masonry-value.enabled", true);
+user_pref("dom.enable_web_task_scheduling", true);
 user_pref("browser.urlbar.groupLabels.enabled", false); // hide firefox suggest label
 user_pref("browser.compactmode.show", true); // add compact mode
 user_pref("browser.tabs.tabmanager.enabled", false); // hide tab manager until needed