feat: add photo

README.md

@@ -6,6 +6,8 @@
 * **Minutes**: Blueish green
 * **Seconds**: Blue
 
+![Photo of the clock with a custom clockface lasercut from a piece of plywood](photo.jpg)
+
 ## Enclosure
 
 The directory `case` contains the [OpenSCAD](https://en.wikibooks.org/wiki/OpenSCAD_User_Manual) project and rendered STL file of the clock's enclosure.
@@ -20,6 +22,8 @@ At the heart of the clock sits an ESP8266, which connects to a WiFi network and
 
 To build the code and program the ESP, you need to install the [PlatformIO](https://platformio.org/) framework.
 
+The WS2812 data line needs to be connected to the ESP's GPIO5 pin.  **Note**: Most breakout boards define their own pin numbers.  For example, with a NodeMCU, GPIO5 corresponds to pin D1.
+
 ```shell-session
 $ git clone https://git.kabelsalat.ch/s3lph/ambient-lighting-clock.git
 $ cd ambient-lighting-clock/esp