Add deployment instructions for Brotli support

Author: clupprich

docs/deployment.md

@@ -1,7 +1,7 @@
 # Deployment
 
 
-Webpacker hooks up a new `webpacker:compile` task to `assets:precompile`, which gets run whenever you run `assets:precompile`. 
+Webpacker hooks up a new `webpacker:compile` task to `assets:precompile`, which gets run whenever you run `assets:precompile`.
 If you are not using Sprockets `webpacker:compile` is automatically aliased to `assets:precompile`. Remember to set NODE_ENV environment variable to production during deployment or when running the rake task.
 
 The `javascript_pack_tag` and `stylesheet_pack_tag` helper method will automatically insert the correct HTML tag for compiled pack. Just like the asset pipeline does it.
@@ -34,15 +34,15 @@ We're essentially doing the following here:
 
 * Creating an app on Heroku
 * Creating a Postgres database for the app (this is assuming that you're using Heroku Postgres for your app)
-* Adding the Heroku NodeJS and Ruby buildpacks for your app. This allows the `npm` or `yarn` executables to properly function when compiling your app - as well as Ruby. 
+* Adding the Heroku NodeJS and Ruby buildpacks for your app. This allows the `npm` or `yarn` executables to properly function when compiling your app - as well as Ruby.
 * Pushing our code to Heroku and kicking off the deployment
 
 
 ## Nginx
 
 Webpacker doesn't serve anything in production. You’re expected to configure your web server to serve files in public/ directly.
 
-Some servers support sending precompressed versions of files with the `.gz` extension when they're available. For example, nginx offers a `gzip_static` directive.
+Some servers support sending precompressed versions of files when they're available. For example, nginx offers a `gzip_static` directive that serves files with the `.gz` extension to supported clients. With an optional module, nginx can also serve Brotli compressed files with the `.br` extension (see below for installation and configuration instructions).
 
 Here's a sample nginx site config for a Rails app using Webpacker:
 
@@ -71,11 +71,24 @@ server {
 
   location ^~ /packs/ {
     gzip_static on;
+    brotli_static on; # Optional, see below
     expires max;
   }
 }
 ```
 
+### Installing the ngx_brotli module
+
+If you wanna serve Brotli compressed files with nginx, you need to install the `nginx_brotli` module. Installation instructions from source can be found in the official [google/ngx_brotli](https://github.com/google/ngx_brotli) repository. Alternatively, depending on your platform, the module might be available via a pre-compiled package.
+
+Once installed, you need to load the module. As we wanna serve pre-compressed files, we only need the static module. Add the following line to your `nginx.conf` file and reload nginx:
+
+```
+load_module modules/ngx_http_brotli_static_module.so;
+```
+
+Now you can set `brotli_static on;` in your nginx site config, per the config in the last section above.
+
 ## CDN
 
 Webpacker out-of-the-box provides CDN support using your Rails app `config.action_controller.asset_host` setting. If you already have [CDN](http://guides.rubyonrails.org/asset_pipeline.html#cdns) added in your Rails app
@@ -106,4 +119,3 @@ namespace :deploy do
   end
 end
 ```
-