Move axum-debug crate to workspace (#497)

* add axum-debug to workspace

* update readme

* add changes to changelog

* little docs update

* fix the gap

a tab has leaked into workspace Cargo.toml, it must be fixed

* address clippy warnings

axum-debug/Cargo.toml

@@ -0,0 +1,16 @@
+[package]
+authors = ["Programatik <[email protected]>"]
+categories = ["development-tools::debugging"]
+description = "Better error messages for axum framework."
+edition = "2018"
+homepage = "https://github.com/tokio-rs/axum"
+keywords = ["axum", "debugging", "debug"]
+license = "MIT"
+name = "axum-debug"
+readme = "README.md"
+repository = "https://github.com/tokio-rs/axum"
+version = "0.1.0"
+
+[dependencies]
+axum = { path = "../axum" }
+axum-debug-macros = { path = "../axum-debug-macros" }