add deployment documentation to web/ directory (#164)

* add deployment documentation to web/ directory

* add clarification

* formatting

web/readme.md

@@ -23,6 +23,20 @@ Web support is available as a technical preview and is only available in the
 
 You should see a message printing the URL to access: `http://localhost:8080`
 
+## Deploying to GitHub Pages
+
+This project uses [peanut][peanut] to build the samples and commit the output
+to the gh-pages branch. To deploy, run these commands in the `web/` directory:
+
+```console
+$ flutter pub global activate peanut
+$ flutter pub global run peanut
+$ git push origin gh-pages:gh-pages
+```
+
+Note: `flutter packages get` must be run in each sample before running `peanut`.
+
 [web]: https://flutter.dev/web
 [samples]: https://flutter.github.io/samples/
+[peanut]: https://github.com/kevmoo/peanut.dart