Add new Ctrl+F shortcut (#125)

usage/keyboard-shortcuts.md

@@ -46,6 +46,11 @@ The Subscription, Trending, and Most Popular Pages have the following shortcuts:
 | ------- | ------------------ |
 | R or F5 | Refresh video list |
 
+Pages with a secondary search bar have the following shortcuts:
+| Key     | Function           |
+| ------- | ------------------ |
+| Command/Ctrl + F | Focus on the secondary search bar |
+
 The FreeTube client can also be controlled with shortcuts you might already be familiar with:
 
 | Key                                            | Function                               |
@@ -66,4 +71,4 @@ The FreeTube client can also be controlled with shortcuts you might already be f
 | Alt + Left Arrow                               | Go back one page                       |
 | Alt + Right Arrow                              | Go forward one page                    |
 
-If you'd like to see even more keyboard shortcuts, consider creating a [feature request](https://github.com/FreeTubeApp/FreeTube/issues/new?assignees=&labels=enhancement&template=feature_request.yaml&title=%5BFeature+Request%5D%3A+).
+If you'd like to see even more keyboard shortcuts, consider creating a [feature request](https://github.com/FreeTubeApp/FreeTube/issues/new?assignees=&labels=enhancement&template=feature_request.yaml&title=%5BFeature+Request%5D%3A+).