Development guidelines about qsharp HOT 2 OPEN

I think the right place to start would be the same place we started with implementation, namely Rust guidance. A lot of this is easy for use (use clippy, CI treats warnings as errors, cargo fmt for code style, etc), but some of it verges more on philosophy (where do we put tests, how do we split up files/modules/crates, etc). Perhaps we can get the low hanging fruit out of the way with itemizing the things we've already put enforcement for in the CI pipeline?

So far, that would be:

• All files must formatted with cargo fmt.
• Crates should use the clippy pedantic top level attribute.
• Additionally, unwrap should be disallowed via the unwrap_use clippy lint.
• Files must remain warning clean, as enforced by -D warnings.

from qsharp.

See also #70

from qsharp.