Add top and height settings for mobile sidebar

The CSS classes for the mobile sidebar changed recently, so use the new
classes. Also set the height of the sidebar appropriately.

This fixes a bug where the sidebar is on top of the hamburger menu,
which prevents closing it once you've opened it.

Author: jsha

templates/style/rustdoc-common.scss

@@ -98,6 +98,16 @@ div.rustdoc {
                     top: $top-navbar-height;
                 }
             }
+
+            // A later version of rustdoc uses the .sidebar.shown instead of .sidebar.mobile, and
+            // also needs a height adjustment.
+            &.shown {
+                width: 250px;
+                margin-left: 0;
+                // 45px is the size of the rustdoc mobile-topbar
+                top: 45px + $top-navbar-height !important;
+                height: calc(100vh - 45px - #{$top-navbar-height}) !important;
+            }
         }
     }