docs: point the book toward its new location with redirects (#2095)

docs/book/README.md

@@ -1,15 +1,3 @@
-This project contains the core of a new introductory guide to Leptos.
-
-It is built using `mdbook`. You can view a local copy by installing `mdbook`
-
-```bash
-cargo install mdbook
-```
-
-and run the book with
-```
-mdbook serve
-```
-
-It should be available at `http://localhost:3000`.
+The Leptos book is now available at [https://book.leptos.dev](https://book.leptos.dev).
 
+The source code for the book has moved to [https://github.com/leptos-rs/book](https://github.com/leptos-rs/book). Please open issues or make PRs in that repository.

docs/book/src/01_introduction.md

@@ -1,22 +1,2 @@
-# Introduction
-
-This book is intended as an introduction to the [Leptos](https://github.com/leptos-rs/leptos) Web framework.
-It will walk through the fundamental concepts you need to build applications,
-beginning with a simple application rendered in the browser, and building toward a
-full-stack application with server-side rendering and hydration.
-
-The guide doesn’t assume you know anything about fine-grained reactivity or the
-details of modern Web frameworks. It does assume you are familiar with the Rust
-programming language, HTML, CSS, and the DOM and basic Web APIs.
-
-Leptos is most similar to frameworks like [Solid](https://www.solidjs.com) (JavaScript)
-and [Sycamore](https://sycamore-rs.netlify.app/) (Rust). There are some similarities
-to other frameworks like React (JavaScript), Svelte (JavaScript), Yew (Rust), and
-Dioxus (Rust), so knowledge of one of those frameworks may also make it easier to
-understand Leptos.
-
-You can find more detailed docs for each part of the API at [Docs.rs](https://docs.rs/leptos/latest/leptos/).
-
-**Important Note**: This current version of the book reflects the `0.5.1` release. The CodeSandbox versions of the examples still reflect `0.4` and earlier APIs and are in the process of being updated.
-
-> The source code for the book is available [here](https://github.com/leptos-rs/leptos/tree/main/docs/book). PRs for typos or clarification are always welcome.
+<meta http-equiv="refresh" content="0; URL=https://book.leptos.dev/">
+<link rel="canonical" href="https://book.leptos.dev/">