This release:

• includes optional support for the ClockworkPi PicoCalc; build and usage instructions are in USING_THE_PICOCALC.md
• adds optional NTP clients for use with zeptoIPv6 (and renames the existing NTP clients for use with zeptoIPv4)
• adds a voltage module to control the voltage regulator on the RP2040 and RP2350
• updates adc::adc-pin to properly configure a given pin on the RP2040 and RP2350 for use with the ADC without requiring any other work on the part of the user
• fixes bugs in zeptoIPv6 which caused crashes