Update 'How to contribute' section

doc/08.appendices.md

@@ -154,23 +154,27 @@ is a markdown (`.md`) file.
 The HTML/CSS is in the `doc/html_in/` directory.
 
 The code is in `steps.diff`, which isn't human-editable. It is generated by a
-program called [leg](https://github.com/yjerem/leg). I will try to document the
-process of editing the `steps.diff` file using `leg` in that repo's `README.md`
-file, soon.
-
-To use `leg` to generate the final static HTML files:
-
-1. You need to have Ruby installed.
-2. `gem install snaptoken` (you may need to `sudo` this).
-3. Inside the `kilo-tutorial` repo, run `leg undiff` to unpack the `steps.diff`
-   file into step folders.
-4. Now you can run `leg doc` to generate the static HTML files in
-   `doc/html_out/`.
-5. When running `leg doc`, each step's diff is cached in a hidden dotfile, so
+program called [leg](https://github.com/yjerem/leg).
+
+If you are making significant changes to the text, you probably want to
+generate the final static HTML files, to preview your changes. Here is how to
+generate the HTML output using the `leg` program:
+
+1. You need to have
+   [Ruby](https://www.ruby-lang.org/en/documentation/installation/) installed.
+2. Install the `leg` binary by running `gem install snaptoken` (you may need to
+   `sudo` this).
+3. Inside the `kilo-tutorial` repo, run `leg doc` to generate the static HTML
+   files in `doc/html_out/` and `doc/html_offline/`.
+4. When running `leg doc`, each step's diff is cached in a hidden dotfile, so
    as long as you're only making changes to files in the `doc/` folder, you can
    run `leg doc -c` to use the cached diffs and regenerate the HTML output way
    faster.
 
+If you just have a small correction to make in the text, there is no need to go
+through all this. Just make the change in the chapter's markdown file and
+[submit a pull request](https://github.com/snaptoken/kilo-tutorial/pulls).
+
 ## Credits
 
 [antirez](http://invece.org/) is the author of