Add bundle-open keybinding to the ruby layer

Also add missing information about `bundler` package to the README.

layers/+lang/ruby/README.org

@@ -11,6 +11,7 @@
    - [[Test runner][Test runner]]
  - [[Key bindings][Key bindings]]
    - [[Ruby (enh-ruby-mode, robe, inf-ruby, ruby-tools)][Ruby (enh-ruby-mode, robe, inf-ruby, ruby-tools)]]
+   - [[Bundler][Bundler]]
    - [[RuboCop][RuboCop]]
    - [[Tests][Tests]]
      - [[RSpec-mode][RSpec-mode]]
@@ -19,6 +20,7 @@
 * Description
 This layer provides support for the Ruby language with the following feature:
 - version manager (rbenv, rvm or chruby)
+- integration with bundler
 - test runner (ruby-test and rspec)
 - linter (rubocop)
 - interactive REPL and code navigation (robe)
@@ -113,6 +115,17 @@ directory local variables.
 | ~SPC m x :~ | Change string to symbol                              |
 | ~%~         | [[https://github.com/redguardtoo/evil-matchit][evil-matchit]] jumps between blocks                    |
 
+** Bundler
+
+| Key binding | Description        |
+|-------------+--------------------|
+| ~SPC b c~   | run bundle check   |
+| ~SPC b i~   | run bundle install |
+| ~SPC b s~   | run bundle console |
+| ~SPC b u~   | run bundle update  |
+| ~SPC b x~   | run bundle exec    |
+| ~SPC b o~   | run bundle open    |
+
 ** RuboCop
 
 | Key binding   | Description                                          |

layers/+lang/ruby/packages.el

@@ -41,7 +41,8 @@
         "bi" 'bundle-install
         "bs" 'bundle-console
         "bu" 'bundle-update
-        "bx" 'bundle-exec))))
+        "bx" 'bundle-exec
+        "bo" 'bundle-open))))
 
 (when (configuration-layer/layer-usedp 'auto-completion)
   (defun ruby/post-init-company ()