docs: add new repo readme welcome image

Signed-off-by: Adam Cooke <adam@krystal.io>

README.md

@@ -1,9 +1,7 @@
-<img src="https://share.adam.ac/21/logo-g3hWemROTemCYbWlmL.svg" width="250" />
+![welcome](https://github.com/postalserver/postal/assets/4765/37e6c405-058a-43c6-be30-7149d873561d)
 
 **Postal** is a complete and fully featured mail server for use by websites & web servers. Think Sendgrid, Mailgun or Postmark but open source and ready for you to run on your own servers. Postal is developed by [Krystal](https://k.io) to serve its own mail processing requirements and we have since decided that it should be released as an open source project for the community.
 
-![Screenshot](https://share.adam.ac/17/k4lA5OuPlU2.png)
-
 * [Documentation](https://docs.postalserver.io)
 * [Installation Instructions](https://docs.postalserver.io/install/prerequisites)
 * [FAQs](https://docs.postalserver.io/welcome/faqs) & [Features](https://docs.postalserver.io/welcome/feature-list)