feat: rewrite huge parts

- real config parsing
- actually working parts, with support for string parts
- handle readonly config (preparation for use with Nix)
- cleanup cli (remove colors, fancy stuff etc., keep it minimal)
- switch to tracing for logging

src/lib.rs

@@ -1,5 +1,6 @@
 #![cfg_attr(docsrs, feature(doc_auto_cfg))]
 #![doc = include_str!("../README.md")]
 
-pub mod cli;
-pub mod utils;
+pub(crate) mod cli;
+pub(crate) mod config;
+pub(crate) mod utils;