help: Offer links to "Keyboard shortcuts" for logged in users.

- Replaces instructions for opening the keyboard shortcuts reference
  with `{relative|gear|keyboard-shortcuts}`.

help/keyboard-shortcuts.md

@@ -232,8 +232,12 @@ A summary of the keyboard shortcuts above is available in the Zulip app.
 
 {start_tabs}
 
-1. Click the **keyboard** (<i class="fa fa-keyboard-o"></i>) icon at the bottom
-   of the app, just below the right sidebar.
+{relative|gear|keyboard-shortcuts}
+
+!!! tip ""
+
+    You can also click the **keyboard** (<i class="fa fa-keyboard-o"></i>)
+    icon at the bottom of the app, just below the right sidebar.
 
 {end_tabs}
 

zerver/lib/markdown/help_relative_links.py

@@ -26,6 +26,7 @@ gear_info = {
     "plans": ["Plans and pricing", "/plans/"],
     "billing": ["Billing", "/billing/"],
     "invite": ["Invite users", "/#invite"],
+    "keyboard-shortcuts": ["Keyboard shortcuts (?)", "/#keyboard-shortcuts"],
     "about-zulip": ["About Zulip", "/#about-zulip"],
 }