update GPIO pins and add note about UPS pins.

docs/setup/gpio.md

@@ -3,24 +3,30 @@
 The photobooth supports Raspberry Pi GPIO to trigger certain events.
 Currently supported triggers are:
 
-- Shutdown host, default GPIO 17, hold 2 seconds
-- Reboot host, default GPIO 18, hold 2 seconds
-- Take a picture, default GPIO 27, press
-- Take a collage, default GPIO 22, press
-- Take an animation (GIF), default GPIO 24, press
-- Print most recent image, default GPIO 23, press
+- Capture actions
+    - Picture, default GPIO 27, press
+    - Collage, default GPIO 22, press
+    - Animation, default GPIO 24, press
+    - Video, default GPIO 25, press
+- Share actions
+    - Print most recent image, default GPIO 23, press
+- System pins
+    - Shutdown host, default GPIO 17, hold 2 seconds
+    - Reboot host, default GPIO 18, hold 2 seconds
+- Reserved otherwise [when using a UPS, controlled by dtoverlays](../extras/ups.md).
+    - Power loss detection, depending on setup, usually GPIO 6
+    - Cut power of UPS, depending on setup, usually GPIO 26
 
 Internally gpiozero python implementation is used.
 
 ## Raspberry Pi GPIO wiring
 
-To use the hardware triggers wire a normally open button from GND to the designated GPIO.
-For example connect the button to GND and GPIO 17.
+To use the hardware triggers wire a normally open button from GND to the designated GPIO (ative low). The photobooth-app enables the Raspberry Pi's internal pull-up resistors if not otherwise noted.
+Example: To shutdown the host connect a button switch to GND and GPIO 17.
 
 ![gpio overview](../assets/GPIO-Pinout-Diagram-2.png)
 <font size="2">[source](https://www.raspberrypi.com/documentation/computers/raspberry-pi.html)</font>
 
 ## Configure
 
-In the admin panel tab hardwareinput enable the GPIO feature in general.
-Change the default GPIO numbers according to your wiring.
+In the admin panel tab `hardwareinput` enable the GPIO feature in general. Then configure the GPIOs in the actions according to your wiring.