Enhancements and fixes planned for 2.3.0 (formerly known as 2.0.1 and then 2.1.0 and briefly 3.1.0)

The main feature targets here are finally implementing low-power library (what was previously called megaTinySleep - that name will not be used) which manages handoff of millis timing between a high frequency clock while the chip is active and a 32.768 kHz clock (either internal ULP or watch crystal) while sleeping, in order to keep time in sleep without accepting the miserable tradeoffs that come with the current RTC millis implementation (mainly sacrificing micros). It will work with the tinyAVR and AVR Dx-series parts.

I'd also like to get the comparator library in, and a couple of digital I/O functions