Add an ability to build assets from Rails root folder

Update README file

README.md

@@ -29,13 +29,16 @@ By default, only `app/assets/stylesheets/application.scss` will be built. If you
 ```
 # config/initializers/dartsass.rb
 Rails.application.config.dartsass.builds = {
-  "app/index.sass"  => "app.css",
-  "site.scss"       => "site.css"
+  "index.sass" => "app.css",
+  "site.scss"  => "site.css"
+  "engines/travel/app/assets/stylesheets/travel/main.scss" => "travel/main.css",
+  "lib/stylesheets/common.css" => "common.css",
 }
 ```
 
 The hash key is the relative path to a Sass file in `app/assets/stylesheets/` and the hash value will be the name of the file output to `app/assets/builds/`.
 
+If file does not exist in `app/assets/stylesheets/` directory - relative path will be changed to `Rails.root`.
 
 ## Version
 

lib/tasks/build.rake

@@ -1,11 +1,15 @@
 EXEC_PATH      = "#{Pathname.new(__dir__).to_s}/../../exe/dartsass"
 CSS_LOAD_PATH  = Rails.root.join("app/assets/stylesheets")
 CSS_BUILD_PATH = Rails.root.join("app/assets/builds")
+CSS_LOAD_FROM_RAILS_ROOT_PATH = Rails.root
 
 def dartsass_build_mapping
-  Rails.application.config.dartsass.builds.map { |input, output| 
-    "#{CSS_LOAD_PATH.join(input)}:#{CSS_BUILD_PATH.join(output)}"
-  }.join(" ")
+  builds_map = Rails.application.config.dartsass.builds.map { |input, output|
+    input_file_path = "#{CSS_LOAD_PATH.join(input)}"
+    input_file_path = "#{CSS_LOAD_FROM_RAILS_ROOT_PATH.join(input)}" unless File.exist?(input_file_path)
+    "#{input_file_path}:#{CSS_BUILD_PATH.join(output)}"
+  }
+  builds_map.uniq.join(" ")
 end
 
 def dartsass_build_options