Add generator templates

lib/templates/rails/generator/%file_name%_generator.rb.tt

@@ -0,0 +1,6 @@
+# frozen_string_literal: true
+
+# License: AGPL-3.0-or-later WITH Web-Template-Output-Additional-Permission-3.0-or-later
+class <%= class_name %>Generator < Rails::Generators::NamedBase
+  source_root File.expand_path('templates', __dir__)
+end

lib/templates/rails/generator/USAGE.tt

@@ -0,0 +1,8 @@
+Description:
+    Explain the generator
+
+Example:
+    bin/rails generate <%= file_name %> Thing
+
+    This will create:
+        what/will/it/create