feat(notification): add confirmation_instructions and new_post

examples/blog/app/views/mailers/notification/confirmation_instructions.html.erb

@@ -0,0 +1,4 @@
+<h1>Confirm your email address</h1>
+<p>Hi <%= user.email %>, welcome to Prism Blog. Please confirm this address is yours.</p>
+<p><a href="<%= confirmation_url %>">Confirm my email</a></p>
+<p>If you didn't sign up, you can ignore this email.</p>