Add the book update guide (#620)

* Update mdbook-open-on-gh version.

2.4.1 would crash during build locally.

* Fix path to async_procs.md.

* Add the guide to update the book.

---------

Co-authored-by: Jacek Sieka <jacek@status.im>

Author: moigagoo

.github/workflows/doc.yml

@@ -26,7 +26,7 @@ jobs:
         run: |
           cargo binstall mdbook@0.4.36 \
             mdbook-toc@0.14.1 \
-            mdbook-open-on-gh@2.4.1 \
+            mdbook-open-on-gh@2.4.3 \
             mdbook-admonish@1.14.0
 
       - uses: jiro4989/setup-nim-action@v1

docs/src/SUMMARY.md

@@ -4,7 +4,7 @@
 # User guide
 
 - [Core concepts](./concepts.md)
-- [`async` functions](async_procs.md)
+- [`async` functions](./async_procs.md)
 - [Errors and exceptions](./error_handling.md)
 - [Threads](./threads.md)
 - [Tips, tricks and best practices](./tips.md)

docs/src/book.md

@@ -0,0 +1,58 @@
+# Updating this book
+
+To contribute to this book, [fork the repository](https://github.com/status-im/nim-chronos/fork), edit the book locally, and [send a pull request](https://github.com/status-im/nim-chronos/compare) with your changes.
+
+## Modifying the content
+
+The book's content is stored in the form of `.md` files in `docs/src` directory. For example, this page's source is at `docs/src/book.md`.
+
+To edit the content, you'll need any text editor and familiarity with [Markdown](https://rust-lang.github.io/mdBook/format/markdown.html) syntax.
+
+If you want to add a new page, edit the file `docs/src/SUMMARY.md`. It's a list of all pages in this book, groupped into parts:
+
+```markdown
+- [Introduction](./introduction.md)
+- [Examples](./examples.md)
+
+# User guide
+
+- [Core concepts](./concepts.md)
+- [`async` functions](./async_procs.md)
+- [Errors and exceptions](./error_handling.md)
+- [Threads](./threads.md)
+- [Tips, tricks and best practices](./tips.md)
+- [Porting code to `chronos`](./porting.md)
+- [HTTP server middleware](./http_server_middleware.md)
+
+# Developer guide
+
+- [Updating this book](./book.md)
+```
+
+If mdBook detects a new page in `SUMMARY.md` that doesn't have a corresponding `.md` file, it will create it automatically during next build and you'll be able to edit it as any other page.
+
+## Building the docs locally
+
+This book is created using [mdBook](https://rust-lang.github.io/mdBook/) so to test your changes locally, you'll need to have it along with preprocessors installed.
+
+If you have a working Rust toolchain set up, install the cargo crates with `cargo install`:
+
+```shell
+cargo install mdbook@0.4.36 mdbook-toc@0.14.1 mdbook-open-on-gh@2.4.3 mdbook-admonish@0.14.0
+```
+
+If you don't have it, the easiest way to install mdBook without installing Rust is to use [cargo-binstall](https://github.com/cargo-bins/cargo-binstall):
+
+```shell
+cargo-binstall mdbook@0.4.36 mdbook-toc@0.14.1 mdbook-open-on-gh@2.4.3 mdbook-admonish@0.14.0
+```
+
+After that, you can build and view the docs locally with this command:
+
+```shell
+mdbook serve --hostname:0.0.0.0 docs
+```
+
+Open [localhost:3000](http://localhost:3000) your browser to see the docs.
+
+`mdbook serve` automatically detects changes in the docs sources, rebuilds the site, and refreshes the page in the browser to show the new version.