Add rufo fixer for ruby files

doc/ale-ruby.txt

@@ -86,5 +86,17 @@ g:ale_ruby_ruby_executable                         *g:ale_ruby_ruby_executable*
   This variable can be changed to use a different executable for ruby.
 
 
+===============================================================================
+rufo                                                            *ale-ruby-rufo*
+
+g:ale_ruby_rufo_executable                         *g:ale_ruby_rufo_executable*
+                                                   *b:ale_ruby_rufo_executable*
+  Type: String
+  Default: `'rufo'`
+
+  Override the invoked rufo binary. This is useful for running rufo from
+  binstubs or a bundle.
+
+
 ===============================================================================
   vim:tw=78:ts=2:sts=2:sw=2:ft=help:norl:

doc/ale.txt

@@ -197,6 +197,7 @@ CONTENTS                                                         *ale-contents*
       reek................................|ale-ruby-reek|
       rubocop.............................|ale-ruby-rubocop|
       ruby................................|ale-ruby-ruby|
+      rufo................................|ale-ruby-rufo|
     rust..................................|ale-rust-options|
       cargo...............................|ale-rust-cargo|
       rls.................................|ale-rust-rls|
@@ -366,7 +367,7 @@ Notes:
 * reStructuredText: `alex`!!, `proselint`, `redpen`, `rstcheck`, `vale`, `write-good`
 * Re:VIEW: `redpen`
 * RPM spec: `rpmlint`
-* Ruby: `brakeman`, `rails_best_practices`!!, `reek`, `rubocop`, `ruby`
+* Ruby: `brakeman`, `rails_best_practices`!!, `reek`, `rubocop`, `ruby`, `rufo`
 * Rust: `cargo`!!, `rls`, `rustc` (see |ale-integration-rust|), `rustfmt`
 * SASS: `sass-lint`, `stylelint`
 * SCSS: `prettier`, `sass-lint`, `scss-lint`, `stylelint`