Add automatic welcome email sender on newsletter subscription

[vansh-codes]

When user subscribes to the newsletter, an automatic welcome email will be shared to the user through the backend server.

This welcome email serves several important purposes:

• Welcome and Acknowledge: It thanks the new subscriber for joining the mailing list and acknowledges their subscription.
• Introduction: It introduces the brand or organization, providing a brief overview of what the subscriber can expect from the newsletter.
• Set Expectations: It outlines the type of content, frequency of emails, and any other relevant details about what the subscriber can expect.
• Engagement: It encourages further engagement, such as following the brand on social media, visiting the website, or exploring popular content.
• Personalization: It often includes personalized content, making the subscriber feel valued and appreciated.

This task would be accomplished using nodemailer library.

[github-actions]

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