Add Readme and picture

README.md

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+Design files for remote controlling an old Onkyo HiFi receiver. Uses a relay, opto-couplers and a 
+Raspberry Pi.
+
+<img src="https://git.lukasschwarz.org/lukas/kbdswitch/media/branch/master/relay2.jpg" width="40%" alt="Picture of a transistor and relay on a PCB, switching power to an amplifier.">
+
+
+[Link to the more detailed article](https://lukasschwarz.org/projects/amp-controller/)