Make this crate no_std

[VictorKoenders]

This crate depends on the following things:

• SerialPort: Can be pulled in a seperate library, or behind a feature flag
• std::io::Write, which is only used to write to a Vec<u8>, which can be replaced by a fixed-size &mut [u8] buffer, embedded-hal::serial::Write or wait for Proposed refactoring to implement core::io rust-lang/rfcs#2262
• Some Vec<u8> and String allocations which can be fixed by having the caller pass a &mut [u8] to the functions