Shorthand URLs: document usage of ::

This adds documentation for redirects such as from
https://docs.rs/clap::Command to the Shorthand URLs page.

Author: zopsicle

templates/core/about/redirections.html

@@ -27,6 +27,11 @@ <h1>Shorthand URLs</h1>
                     <td>Latest version of clap</td>
                 </tr>
 
+                <tr>
+                    <td><a href="https://docs.rs/clap::Command">docs.rs/clap::Command</a></td>
+                    <td>Latest version of clap, and search for "Command" within the crate</td>
+                </tr>
+
                 <tr>
                     <td>
                         <a href="https://docs.rs/clap/%7E2">docs.rs/clap/~2</a>