* Move axum crate into workspace subfolder
Over time I imagine we're gonna have other crates in this repo that
provide utilities or integrations for axum. This prepares for that by
moving the main axum crate into its own folder.
The README situation is a bit annoying because we want `./README.md`
for viewing the repo on github but `axum/README.md` for crates.io. For
now I've just copy/pasted it and added CI step to make sure they're
identical.
* update changelog link
* Add licenses to all examples
* is this how you install `diff`?
* or maybe this is how?
* fix readme links
* like this?
* fix cargo-deny step
* Try making root readme a symlink
* remove compare readme step
not needed since readme in repo root is now a symlink
* Revert "Add licenses to all examples"
This reverts commit ab321b7fb9.
With https://github.com/tokio-rs/axum/pull/404 and https://github.com/tokio-rs/axum/pull/402 all routes now have the same types and thus we don't need to nest them but can instead store them all in a map. This simplifies the routing quite a bit and is faster as well.
High level changes:
- Routes are now stored in a `HashMap<RouteId, Route<B>>`.
- `Router::or` is renamed to `Router::merge` because thats what it does now. It copies all routes from one router to another. This also means overlapping routes will cause a panic which is nice win.
- `Router::merge` now only accepts `Router`s so added `Router::fallback` for adding a global 404 handler.
- The `Or` service has been removed.
- `Router::layer` now only adds layers to the routes you actually have meaning middleware runs _after_ routing. I believe that addresses https://github.com/tokio-rs/axum/issues/380 but will test that on another branch.
This way there is now only one way to create a router:
```rust
use axum::{Router, handler::get};
let app = Router::new()
.route("/foo", get(handler))
.route("/foo", get(handler));
```
`nest` was changed in the same way:
```rust
use axum::Router;
let app = Router::new().nest("/foo", service);
```
