Reorganize README.md. (#16)

The main instructions for using Eyra are now simple enough (just two
steps!) that it makes sense to have that be the "quick start", and to
move the link to the hello world example below that.

README.md

@@ -24,12 +24,6 @@ ABI-compatible libc function implementations.
 
 ## Quick start
 
-Check out [this hello world example].
-
-[this hello world example]: https://github.com/sunfishcode/eyra/tree/main/example-crates/hello-world/
-
-## In detail
-
 Eyra needs two things. First, a Cargo.toml dependency, which we can add with:
 
 ```console
@@ -50,6 +44,12 @@ Linux, this crate prints "Hello, world!". And under the covers, it uses
 [Origin] to start and stop the program, [c-ward] to handle libc calls from
 `std`, and [rustix] to do the printing, so it's completely implemented in Rust.
 
+## Example
+
+For an example of the above steps, check out [this hello world example].
+
+[this hello world example]: https://github.com/sunfishcode/eyra/tree/main/example-crates/hello-world/
+
 ## Optional logging
 
 Eyra has a `log` feature to enable Rust `log` tracing of program and thread