doc: add remark about wing angles wrong zero

arduinoFiles/README.md

-# MechaRaptor - Arduino data, 2022
+# MechaRaptor - Arduino
 
 The data are automatically sorted by year, month and day.
 See the various identification csv files are the root of the repository to know
 what they are linked to.
 
+## Important notes
+
+- **DO NOT USE THE WING ANGLES IN DEGREE**. The zeroing of the angles was not
+  properly made. Therefore only the raw wing angles should be considered and
+  remapped properly in post-processing.
+
 ---
 
 title: MechaRaptor - Arduino Data, 2022