Add `p b` to the shortcuts documentation

Signed-off-by: Rémy Coutable <remy@rymai.me>

app/views/help/_shortcuts.html.haml

@@ -30,7 +30,7 @@
                 %tr
                   %td.shortcut
                     .key p b
-                  %td Enable the Performance Bar
+                  %td Show/hide the Performance Bar
                 %tr
                   %td.shortcut
                     .key ?

doc/workflow/shortcuts.md

@@ -6,7 +6,10 @@ You can see GitLab's keyboard shortcuts by using 'shift + ?'
 
 | Keyboard Shortcut | Description |
 | ----------------- | ----------- |
+| <kbd>n</kbd> | Main navigation |
 | <kbd>s</kbd> | Focus search |
+| <kbd>f</kbd> | Focus filter |
+| <kbd>p b</kbd> | Show/hide the Performance Bar |
 | <kbd>?</kbd> | Show/hide this dialog |
 | <kbd>⌘</kbd> + <kbd>shift</kbd> + <kbd>p</kbd> | Toggle markdown preview |
 | <kbd>↑</kbd> | Edit last comment (when focused on an empty textarea) |