refactor lib.rs into modules

split the lib.rs main file into submodules for easier navigation and separation of concerns:

lib.rs
rawsmallvec.rs
taggedlen.rs
serde.rs
drain.rs
extractif.rs
...
...

the modules should have clear API boundaries, no ad-hoc splitting. e.g.:

key rule: a file has one purpose and touches one part of the code

key rule: if you have to make a mod {/*...*/} item, then it probably should be its own file

ideally this should be done after merging #387

Navigation Menu