Allow embedding config in rast-agent for release

[seqre]

For embedding config in prod and loading in dev for the agent, this flag will be of use: https://doc.rust-lang.org/reference/conditional-compilation.html#debug_assertions

Possible implementation: https://github.com/pyrossh/rust-embed/blob/master/src/lib.rs

Originally posted by @seqre in https://github.com/seqre/rast/issues/4#issuecomment-1272427892