add CONTRIBUTING.md (#292)

CONTRIBUTING.md

@@ -0,0 +1,32 @@
+# Contributing to the Anki manual
+
+## Local development
+
+anki-manual is built using [mdBook](https://rust-lang.github.io/mdBook/), a Rust-based tool for creating webpages using Markdown.
+
+### Install dependencies
+
+In order to use mdBook, please first ensure that you have [Rust](https://www.rust-lang.org/tools/install) installed on your machine.
+
+Next, install mdBook and its pre-processors
+```
+cargo install mdbook
+cargo install mdbook-toc
+cargo install mdbook-linkcheck
+```
+
+### Develop and preview
+
+To serve anki-manual locally, build the book with
+
+```
+mdbook build
+```
+
+and then serve anki-manual with
+
+```
+mdbook serve --open
+```
+
+You can now make changes to the markdown (*.md) files in the `src/` directory and have your changes previewed locally.

README.md

@@ -5,4 +5,4 @@ This manual is licensed under the CC BY-SA 4 license:
 https://creativecommons.org/licenses/by-sa/4.0/
 
 Pull requests are welcome. Unless you state otherwise, any pull requests you
-submit will be licensed under the above license.
+submit will be licensed under the above license. Please see [CONTRIBUTING](CONTRIBUTING.md) for more details.