add sendgrid example

nodemailer/sendgrid.mjs

@@ -0,0 +1,21 @@
+import nodemailer from "nodemailer";
+
+// see https://support.sendgrid.kke.co.jp/hc/ja/articles/204187885-SMTP%E3%81%AE%E6%8E%A5%E7%B6%9A%E6%83%85%E5%A0%B1%E3%82%92%E6%95%99%E3%81%88%E3%81%A6%E3%81%8F%E3%81%A0%E3%81%95%E3%81%84-
+const transporter = nodemailer.createTransport({
+  host: "smtp.sendgrid.net",
+  port: 465,
+  secure: true,
+  auth: {
+    user: "apikey",
+    pass: "SG.****", // https://app.sendgrid.com/settings/api_keys > Create API Key > Mail Send > Custom Access > Mail Send
+  },
+});
+
+const info = await transporter.sendMail({
+  from: "foo@example.org",
+  to: "bar@example.org",
+  subject: "Hello world!",
+  html: "<marquee>Hello world.</marquee>",
+});
+
+console.log(info.messageId);