add wire colours as images, as well

Gitlab doesn't render the colors. I assume this is because it removes
the styles when sanitizing the HTML, which is sort-of reasonable
(except it could inspect them deeper and see that these are harmless).

README.md

@@ -181,6 +181,8 @@ Option 1: This is similar to our first, intuitive idea but with two power lines
 </tr>
 </table>
 
+![wire colors, option 1](./img/wires-option1.png)
+
 Option 2: WS2812 signal on center wire. This is not such a good match for intuition (blue is a signal and pink is GND) but all influences should cancel out and the central wire is not a power wire (i.e. doesn't get warm). This makes the most sense from a technical perspective.
 
 <table style="border: none !important; border-collapse: separate; text-align: center">
@@ -212,6 +214,8 @@ Option 2: WS2812 signal on center wire. This is not such a good match for intuit
 </tr>
 </table>
 
+![wire colors, option 2](./img/wires-option2.png)
+
 
 Zusätzliche Nutzung
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