Set Rails Engine/Gem public assets path, to server it from Engine/Gem itself

gistfile1.rb

require "rails"

module MyEngine
  class Engine < Rails::Engine
     
    # We can add all of the public assets from our engine and make them
    # available to use.  This allows us to use javascripts, images, stylesheets
    # etc.
    initializer "static assets" do |app|
      app.middleware.insert_before(::ActionDispatch::Static, ::ActionDispatch::Static, "#{root}/public")
    end
  end
end