Added note for archiving purposes

I added a note as discussed in the #16 . This repo should be archived as it has been superseded by the Arduino Science Journal library

Author: jhansson-ard

README.md

@@ -1,5 +1,7 @@
 # PhysicsLabFirmware library for Arduino
 
+**Note:** This library has been superseded by [arduino-libraries/Arduino_ScienceJournal](https://github.com/arduino-libraries/Arduino_ScienceJournal).
+
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