Add support for Rails 5.

Giving this another go, since I need this in order to add tailwindcss
generator for the `view_component`.

View component is `rails >= 5`

Author: dixpac

Gemfile.lock

@@ -2,7 +2,7 @@ PATH
   remote: .
   specs:
     tailwindcss-rails (0.5.1)
-      rails (>= 6.0.0)
+      rails (>= 5.0.0)
 
 GEM
   remote: https://rubygems.org/

tailwindcss-rails.gemspec

@@ -13,5 +13,5 @@ Gem::Specification.new do |spec|
 
   spec.files = Dir["{app,lib}/**/*", "MIT-LICENSE", "Rakefile", "README.md"]
 
-  spec.add_dependency "rails", ">= 6.0.0"
+  spec.add_dependency "rails", ">= 5.0.0"
 end