Fix commonmark Markdown warnings in docs, part 1

Fixes warnings from rust-lang/rust#44229 when `--enable-commonmark` is
passed to rustdoc.

This is mostly a global find-and-replace for bare URIs on lines by
themselves in doc comments.

components/script_traits/script_msg.rs

@@ -137,7 +137,7 @@ pub enum ScriptMsg {
     /// Scroll a page in a window
     ScrollFragmentPoint(ClipId, Point2D<f32>, bool),
     /// Set title of current page
-    /// https://html.spec.whatwg.org/multipage/#document.title
+    /// <https://html.spec.whatwg.org/multipage/#document.title>
     SetTitle(Option<String>),
     /// Send a key event
     SendKeyEvent(Option<char>, Key, KeyState, KeyModifiers),