Add method to render template to string instead of a file

[bogdan]

Sometimes rendering a template to file doesn't have enough flexibility and it is better to render template to string and then put content to file manually via inject_into_file etc.
As a bonus, this method can be easier to use to test templates.

Here is the draft from ChatGPT of what is needed:

    # Renders an ERB template from the source path and returns it as a string.
    #
    # ==== Parameters
    # source<String>:: the relative path to the source root.
    # context<Binding>:: binding context for the template (default: instance_eval binding).
    #
    # ==== Returns
    # String:: the rendered template content.
    #
    # ==== Example
    #   render_template("README")
    #
    def render_template(source, context: instance_eval("binding"))
      source = File.expand_path(find_in_source_paths(source.to_s))
      capturable_erb = CapturableERB.new(::File.binread(source), trim_mode: "-", eoutvar: "@output_buffer")
      capturable_erb.tap { |erb| erb.filename = source }.result(context)
    end

    # Gets an ERB template at the relative source, executes it, and makes a copy
    # at the relative destination. If the destination is not given it's assumed
    # to be equal to the source removing .tt from the filename.
    #
    # ==== Parameters
    # source<String>:: the relative path to the source root.
    # destination<String>:: the relative path to the destination root.
    # config<Hash>:: give :verbose => false to not log the status.
    #
    # ==== Examples
    #
    #   template "README", "doc/README"
    #
    #   template "doc/README"
    #
    def template(source, *args, &block)
      config = args.last.is_a?(Hash) ? args.pop : {}
      destination = args.first || source.sub(/#{TEMPLATE_EXTNAME}$/, "")
      content = render_template(source, context: config.delete(:context) || instance_eval("binding"))
      content = yield(content) if block
      create_file destination, nil, config { content }
    end

[rafaelfranca]

Makes sense to me. Do you want to open a PR?