Change sass cli params to permit multiple inputs

The sass cli allows for multiple sources & outputs - using the source:destination syntax makes this more obvious if a user wanted to bundle multiple sources at once

Author: acallaghan

lib/install/bootstrap/install.rb

@@ -17,7 +17,7 @@
 end
 
 say "Add build:css script"
-build_script = "sass ./app/assets/stylesheets/application.bootstrap.scss ./app/assets/builds/application.css --no-source-map --load-path=node_modules"
+build_script = "sass ./app/assets/stylesheets/application.bootstrap.scss:./app/assets/builds/application.css --no-source-map --load-path=node_modules"
 
 if (`npx -v`.to_f < 7.1 rescue "Missing")
   say %(Add "scripts": { "build:css": "#{build_script}" } to your package.json), :red

lib/install/bulma/install.rb

@@ -4,7 +4,7 @@
 run "yarn add sass bulma"
 
 say "Add build:css script"
-build_script = "sass ./app/assets/stylesheets/application.bulma.scss ./app/assets/builds/application.css --no-source-map --load-path=node_modules"
+build_script = "sass ./app/assets/stylesheets/application.bulma.scss:./app/assets/builds/application.css --no-source-map --load-path=node_modules"
 
 if (`npx -v`.to_f < 7.1 rescue "Missing")
   say %(Add "scripts": { "build:css": "#{build_script}" } to your package.json), :red

lib/install/sass/install.rb

@@ -3,7 +3,7 @@
 run "yarn add sass"
 
 say "Add build:css script"
-build_script = "sass ./app/assets/stylesheets/application.sass.scss ./app/assets/builds/application.css --no-source-map --load-path=node_modules"
+build_script = "sass ./app/assets/stylesheets/application.sass.scss:./app/assets/builds/application.css --no-source-map --load-path=node_modules"
 
 if (`npx -v`.to_f < 7.1 rescue "Missing")
   say %(Add "scripts": { "build:css": "#{build_script}" } to your package.json), :red