Update prefs.js

Firefox/prefs.js

@@ -109,4 +109,7 @@ user_pref("toolkit.telemetry.reportingpolicy.firstRun", false);
 user_pref("trailhead.firstrun.didSeeAboutWelcome", true);
 user_pref("xpinstall.signatures.required", false);
 user_pref("full-screen-api.macos-native-full-screen", true);
+user_pref("browser.cache.memory.enable", true);
+user_pref("gfx.webrender.all", true);
+user_pref("gfx.webrender.software", false);