WIP no_std

[Ygg01]

Motivation

We want to use simd_json in no_std environments. So we introduce no_std and refactor a bit.

What went wrong?

Just about everything.

value_trait crate is std only

It uses io: Write throughout to define bounds. Which is fine, but without it being no_std this crate has no chance to be std

Lots of println! macros

Yeah, those don't work if you don't have output.

Hard to separate no_std and std boundary.

I honestly prefer multiple crates per workspace and then deal with all crates in a single folder.

Next moves

Best way to approach IMO is:

1. Convert this single repository to a workspace
2. Move value_trait crate in.
   a. Add std feature (possibly breaking change) to value_trait
   b. In std feature use std::io, otherwise use embedded_io crate
   c. bump major version and publish.
3. Move io components to a crate that imports the no_std version simd-lite-core crate is my goto, but i can settle for
4. Bump major version.

Fix #92 when it actually lands.