B2B-88: add starter kit structure and elements

packages/mailers/shared/src/mailer.ts

@@ -0,0 +1,7 @@
+import { z } from 'zod';
+
+import { MailerSchema } from './schema/mailer.schema';
+
+export abstract class Mailer<Res = unknown> {
+  abstract sendEmail(data: z.infer<typeof MailerSchema>): Promise<Res>;
+}