v1.0.1
 - initial version

v1.0.2
 - fixed typo in conditional compilation

v1.0.3
 - added a few missed MCUs
 - added badges in readme file
 - added CI workflow
 - corrected ATmega8 measurements

v1.1.0 (03.06.2023)
 - added internal _intref variable that has higher priority than the
   EEPROM value
 - added setIntref method that can be used to set the value

v1.1.1 (03.06.2023)
 - added keyword in keywords.txt

v2.0.0 (25.06.2023)
 - changed interface in EEPROM: E2END-3..E2END-2: intref (-1 meaning
   no value). The remaining values are used as follows: E2END-1: OSCCAL value is valid, E2END: OSCCAL
   calibration value. This is at least what the avrCalibrate library uses.
 - removed ATtiny43U since the test board I own did not give
   meaningful results - more work is necessary here
 - added ATtiny26

v2.1.0 (26.06.2023)
 - added ATmega16, 32, 8535

v2.2.0 (27.06.2023)
 - new constant DEFAULT_INTREF, which is the default internal
   reference voltage

v2.3.1 (31.12.2025)
 - added a few more MCUs
