Integrate the boot menu key animation (#10649)

wiki/src/install/inc/steps/pc_boot_menu.inline.html

@@ -87,6 +87,12 @@ following screenshot is an example of such boot menu:</p>
 
 </ol>
 
+<p>This animation explains how to use the boot menu key:</p>
+
+<video controls width="640" height="360" poster="https://tails.boum.org/install/inc/videos/boot-menu-key.png">
+  <source src="https://tails.boum.org/install/inc/videos/boot-menu-key.webm" type="video/webm">
+</video>
+
 <h3>Check our list of known issues</h3>
 
 <p>Similar problems might have been reported already for your model of computer