feat: Add initial support to pub/sub

- Client subscription
- refactor: Move as much as possible out of `mod.rs` files
- refactor: Move some client logic into a Tower Service
- docs: Add extra doc strings
- docs: Move top level docs into `src/lib.rs`
- docs: Add a http server to preview the docs
- remove Cargo.lock from main library

.gitignore

@@ -1,2 +1,4 @@
 /target
 .vim/
+.DS_Store
+/Cargo.lock