firefox: add a userContent.css

dotfiles/firefox.css

@@ -0,0 +1,23 @@
+/* To be symlinked in Firefox profile as chrome/userContent.css */
+
+@-moz-document domain(twitter.com) {
+    html {
+        scroll-snap-type: y mandatory !important;
+    }
+
+    /* Tweets in the timeline are <article> elements */
+    article {
+        scroll-snap-align: start !important;
+    }
+
+    /* Un-stick the sticky header and make it “snappable” as well */
+    [aria-label="Home timeline"] > :first-child {
+        position: static !important;
+        scroll-snap-align: start !important;
+    }
+
+    /* Hide the “new Tweets available” floating toast notification */
+    [aria-label="New Tweets are available."] {
+        display: none !important;
+    }
+}

dotfiles/firefox.js

@@ -79,3 +79,6 @@ user_pref("browser.safebrowsing.malware.enabled", false);
 
 // Don't trim URLs
 user_pref("browser.urlbar.trimURLs", false);
+
+// Enable userContent.css
+user_pref("toolkit.legacyUserProfileCustomizations.stylesheets", true);