docs: link to book (#286)

* docs: explain diff between `docs` and `book`

* docs: link to book

README.md

@@ -12,8 +12,10 @@ Rust minimum required version to build this project is 1.65.0 published 02.11.20
 
 ## Docs
 
-Contributor docs can be found [here](./docs).
+- [User docs][book]
+- [Contributor docs](./docs)
 
 [codecov]: https://app.codecov.io/gh/foundry-rs/reth
 [gh-ci]: https://github.com/foundry-rs/reth/actions/workflows/ci.yml
 [gh-deny]: https://github.com/foundry-rs/reth/actions/workflows/deny.yml
+[book]: https://foundry-rs.github.io/reth/

docs/repo/layout.md

@@ -2,6 +2,10 @@
 
 This repository contains several Rust crates that implement the different building blocks of an Ethereum node. The high-level structure of the repository is as follows:
 
+### Documentation
+
+Contributor documentation is in [`docs`](../../docs) and end-user documentation is in [`book`](../../book).
+
 ### Binaries
 
 All binaries are stored in [`bin`](../../bin).