Feature/17 newsletters

[kevmhughes]

This pull request integrates the newsletter functionality into the main branch. The changes include:

• Added necessary dependencies to package.json for newsletter functionality: mailchimp, node-cron, and nodemailer.
• Added two new routes in index.routes.js.
• Created email.template.js for email template management.
• Created email.services.js to encapsulate the logic for handling the newsletter functionality.
• Updated env.examplewith examples of required environment variables.
• Removed unused variable declarations.
• Added temporary basic html form on home.ejs to test /subscribe endpoint.

No merge conflicts were encountered.

[MariaChmielinska]

Review: emailing function was tested. result: emails received subscribe function as well. result: subscribed and unsubscribed successfully.