Add support for Brotli compression (#2273)

docs/deployment.md

@@ -42,7 +42,7 @@ We're essentially doing the following here:
 
 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:
 
@@ -79,12 +79,25 @@ server {
 
   location ^~ /packs/ {
     gzip_static on;
+    brotli_static on; # Optional, see below
     expires max;
     add_header Cache-Control public;
   }
 }
 ```
 
+### Installing the ngx_brotli module
+
+If you want to serve Brotli compressed files with nginx, you will 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) git 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 want to serve the 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, as 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
@@ -115,4 +128,3 @@ namespace :deploy do
   end
 end
 ```
-

package/environments/production.js

@@ -18,6 +18,18 @@ module.exports = class extends Base {
       })
     )
 
+    if ('brotli' in process.versions) {
+      this.plugins.append(
+        'Compression Brotli',
+        new CompressionPlugin({
+          filename: '[path].br[query]',
+          algorithm: 'brotliCompress',
+          cache: true,
+          test: /\.(js|css|html|json|ico|svg|eot|otf|ttf|map)$/
+        })
+      )
+    }
+
     this.plugins.append(
       'OptimizeCSSAssets',
       new OptimizeCSSAssetsPlugin({