Update banner image (#232)

Author: ZIJ

README.md

@@ -1,6 +1,5 @@
-<h1 align="center">
-  <img width="733" alt="Screenshot 2023-02-28 at 11 25 48" src="https://user-images.githubusercontent.com/1280498/221849642-ae6cb056-5b5b-478f-8cfb-42790e1739e7.png">
-</h1>
+<img width="1470" alt="digger-opensource-gitops-banner" src="https://github.com/diggerhq/digger/assets/1280498/7fb44db3-38ca-4021-8714-87a2f1a14982">
+
 <h2 align="center">
   <a href="https://join.slack.com/t/diggertalk/shared_invite/zt-1tocl4w0x-E3RkpPiK7zQkehl8O78g8Q">Slack</a> |
   <a href="https://digger.dev">Website</a> |