web: Add missing CSS.escape calls.

When referring to <div id="my-id" class="my-class">:

- my-id is an id
- #my-id is a selector
- my-class is a class name
- .my-class is a selector

When an id or a class name is interpolated into a selector, it needs
to be escaped with CSS.escape.

Signed-off-by: Anders Kaseorg <anders@zulip.com>

web/src/stream_edit.js

@@ -267,7 +267,7 @@ export function setup_stream_settings(node) {
         ],
         callback(name, key) {
             $(".stream_section").hide();
-            $("." + key).show();
+            $(`.${CSS.escape(key)}`).show();
             select_tab = key;
         },
     });