Bug 1349256 - Added docs about how to generate the gitbook; r=sole

MozReview-Commit-ID: 9pa0rXaLehZ

--HG--
extra : rebase_source : dc5b2d51990bf7cfd0bf56241b69189598b9b9c6

devtools/docs/README.md

@@ -6,4 +6,19 @@ If you are looking for general docs about how to use the tools, checkout [this M
 
 If you are looking for a getting started guide on the developer tools, all of this information is documented on the [Hacking](https://wiki.mozilla.org/DevTools/Hacking) wiki page.
 
-Head over to the [table of contents](SUMMARY.md) to browse the documentation.
+[GitBook](https://github.com/GitbookIO/gitbook) is used to generate online documentation from the markdown files here.
+Here is how you can re-generate the book:
+
+```bash
+# Install GitBook locally
+npm install -g gitbook-cli
+
+# Go into the docs directory
+cd /path/to/mozilla-central/devtools/docs/
+
+# Generate the docs and start a local server
+gitbook serve
+
+# Or just built the book
+gitbook build
+```