feat: add "resend" email sending notification provider

[lsnnt]

📝 Summary of changes done and why they are done

The new notification provider is added and also tested using my own domains and api keys

📋 Related issues

N/A

📄 Checklist

Please follow this checklist to avoid unnecessary back and forth (click to expand)

• ⚠️ If there are Breaking change (a fix or feature that alters existing functionality in a way that could cause issues) I have called them out
• 🔍 My code adheres to the style guidelines of this project.
• 🦿 I have indicated where (if any) I used an LLM for the contributions
• ✅ I ran ESLint and other code linters for modified files.
• ⚠️ My changes generate no new warnings.
• 🛠️ I have reviewed and tested my code.
• 📝 I have commented my code, especially in hard-to-understand areas (e.g., using JSDoc for methods).
• 🤖 My code needed automated testing. I have added them (this is an optional task).
• 📄 Documentation updates are included (if applicable).
• 🔒 I have considered potential security impacts and mitigated risks.
• 🧰 Dependency updates are listed and explained.

📷 Screenshots or Visual Changes

N/A

[lsnnt]

One of the CI jobs failed due to a temporary network issue (Connection failed in TCP test).
Could you please re-run the checks?

[CommanderStorm]

Nice work.

I’d like to see this made resilient against XSS in emails, or alternatively switched to plain-text emails.

More generally, adding templating support could be a nice improvement for the notification provider and shouldn’t require much additional code. That said, if you’d rather not take this on, that’s perfectly fine too.

[CommanderStorm]

Nice work, thank you ❤️