update readme: fix link of fixing jpg for 0.9 errata

readme.md

@@ -19,5 +19,5 @@ There is a mistake with the output power switching in revision `0.9` – gladly
 
 The footprint of the hexinverter chip had the in- and outputs of the right side swapped. Fix: using some resistor legs like this:
 
-![](images/0.9_fix_40106.png)
+![](images/0.9_fix_40106.jpg)