help: Document = keyboard shortcut.

Documents the new shortcut in the `?` menu, Keyboard Shortcuts page,
and Emoji Reactions page.

help/emoji-reactions.md

@@ -51,6 +51,11 @@ message.
     To make it easy to see which reactions you have added, they are
     highlighted in a different color.
 
+!!! keyboard_tip ""
+
+    You can also toggle the first emoji reaction on the selected message by
+    using the <kbd>=</kbd> shortcut.
+
 {tab|mobile}
 
 1. Click on an existing emoji reaction to add or remove your reaction.

help/keyboard-shortcuts.md

@@ -156,6 +156,8 @@ in the Zulip app to add more to your repertoire as needed.
   src="/static/generated/emoji/images/emoji/unicode/1f44d.png"
   title="thumbs up"/>**: <kbd>+</kbd>
 
+* **Toggle first emoji reaction**: <kbd>=</kbd>
+
 * **Mark as unread from selected message**: <kbd>Shift</kbd> + <kbd>U</kbd>
 
 * **Collapse/show message**: <kbd>-</kbd>

web/templates/keyboard_shortcuts.hbs

@@ -242,6 +242,10 @@
                     </td>
                     <td><span class="hotkey"><kbd>+</kbd></span></td>
                 </tr>
+                <tr>
+                    <td class="definition">{{t 'Toggle first emoji reaction on selected message' }}</td>
+                    <td><span class="hotkey"><kbd>=</kbd></span></td>
+                </tr>
                 <tr>
                     <td class="definition">{{t 'Mark as unread from selected message' }}</td>
                     <td><span class="hotkey"><kbd>Shift</kbd> + <kbd>U</kbd></span></td>