wish: publish at crates.io

[stappersg]

Currently this

$ AVR_CPU_FREQUENCY_HZ=8_000_000 cargo +nightly publish --target ./avr-atmega328p.json -Z build-std=core
    Updating crates.io index
   Packaging ruduino v0.4.0 (/home/gs0604/src/rust/RustAVR/ruduino)
error: failed to prepare local package for uploading

Caused by:
  failed to select a version for the requirement `avr_delay = "^0.4.0"`
  candidate versions found which didn't match: 0.3.2, 0.3.1, 0.3.0, ...
  location searched: crates.io index
  required by package `ruduino v0.4.0 (/home/stappers/src/rust/RustAVR/ruduino)`

I think the

  failed to select a version for the requirement `avr_delay = "^0.4.0"`
  candidate versions found which didn't match: 0.3.2, 0.3.1, 0.3.0, ...

means that avr-rust/delay#21 has to fixed first ...