Add videos for pinch-to-zoom and tilt

A video is worth a thousand words.

doc/control.md

@@ -67,8 +67,12 @@ More precisely, hold down <kbd>Ctrl</kbd> while pressing the left-click button.
 Until the left-click button is released, all mouse movements scale and rotate
 the content (if supported by the app) relative to the center of the screen.
 
+https://github.com/Genymobile/scrcpy/assets/543275/26c4a920-9805-43f1-8d4c-608752d04767
+
 To simulate a tilt gesture: <kbd>Shift</kbd>+_click-and-move-up-or-down_.
 
+https://github.com/Genymobile/scrcpy/assets/543275/1e252341-4a90-4b29-9d11-9153b324669f
+
 Technically, _scrcpy_ generates additional touch events from a "virtual finger"
 at a location inverted through the center of the screen. When pressing
 <kbd>Ctrl</kbd> the _x_ and _y_ coordinates are inverted. Using <kbd>Shift</kbd>