[docs] Mention bundler flags/configs for ruby projects (#1031)

## Summary

## How was it tested?

Author: mauricioabreu

docs/app/docs/devbox_examples/languages/ruby.md

@@ -6,7 +6,7 @@ title: Ruby
 
 [![Open In Devbox.sh](https://jetpack.io/img/devbox/open-in-devbox.svg)](https://devbox.sh/github.com/jetpack-io/devbox?folder=examples/development/ruby)
 
-Ruby can be automatically configured by Devbox via the built-in Ruby Plugin. This plugin will activate automatically when you install Ruby 2.7 using `devbox add ruby`. 
+Ruby can be automatically configured by Devbox via the built-in Ruby Plugin. This plugin will activate automatically when you install Ruby 2.7 using `devbox add ruby`.
 
 ## Adding Ruby to your shell
 
@@ -19,9 +19,9 @@ Run `devbox add ruby bundler`, or add the following to your `devbox.json`
     ]
 ```
 
-This will install Ruby 3.1 to your shell. 
+This will install Ruby 3.1 to your shell.
 
-Other versions available include:  
+Other versions available include:
 
 * `ruby` (Ruby 2.7)
 * `ruby_3_0` (Ruby 3.0)
@@ -40,3 +40,13 @@ GEMRC={PROJECT_DIR}/.devbox/virtenv/ruby/.gemrc
 GEM_HOME={PROJECT_DIR}/.devbox/virtenv/ruby
 PATH={PROJECT_DIR}/.devbox/virtenv/ruby/bin:$PATH
 ```
+
+## Bundler
+
+In case you are using bundler to install gems, bundler config file can still be used to pass configs and flags to install gems.
+
+`.bundle/config` file example:
+
+```
+BUNDLE_BUILD__SASSC: "--disable-lto"
+```