Add rake tasks

Rakefile

@@ -10,3 +10,15 @@ Rake::TestTask.new(:test) do |t|
 end
 
 task default: :test
+
+namespace :rbs do
+  task :generate do
+    sh "rbs-inline --opt-out --output lib"
+  end
+
+  task :watch do
+    sh "fswatch -0 lib | xargs -n1 -0 rbs-inline --opt-out --output lib"
+  rescue Interrupt
+    # nop
+  end
+end