Add support for Packwerk (#4594)

Packwerk (https://github.com/Shopify/packwerk) is a Ruby gem
used to enforce boundaries and modularize Rails applications.

doc/ale-ruby.txt

@@ -48,6 +48,26 @@ g:ale_ruby_debride_options                         *g:ale_ruby_debride_options*
   This variable can be changed to modify flags given to debride.
 
 
+===============================================================================
+packwerk                                                    *ale-ruby-packwerk*
+
+g:ale_ruby_packwerk_executable                 *g:ale_ruby_packwerk_executable*
+                                               *b:ale_ruby_packwerk_executable*
+  Type: |String|
+  Default: `'packwerk'`
+
+  Override the invoked packwerk binary. Set this to `'bundle'` to invoke
+  `'bundle` `exec` packwerk'.
+
+
+g:ale_ruby_packwerk_options                       *g:ale_ruby_packwerk_options*
+                                                  *b:ale_ruby_packwerk_options*
+  Type: |String|
+  Default: `''`
+
+  This variable can be changed to modify flags given to packwerk.
+
+
 ===============================================================================
 prettier                                                    *ale-ruby-prettier*
 

doc/ale-supported-languages-and-tools.txt

@@ -547,6 +547,7 @@ Notes:
   * `brakeman`!!
   * `cspell`
   * `debride`
+  * `packwerk`!!
   * `prettier`
   * `rails_best_practices`!!
   * `reek`

doc/ale.txt

@@ -3324,6 +3324,7 @@ documented in additional help files.
     brakeman..............................|ale-ruby-brakeman|
     cspell................................|ale-ruby-cspell|
     debride...............................|ale-ruby-debride|
+    packwerk..............................|ale-ruby-packwerk|
     prettier..............................|ale-ruby-prettier|
     rails_best_practices..................|ale-ruby-rails_best_practices|
     reek..................................|ale-ruby-reek|