Update README with new logo banner

[mcturco]

Reason/Context

This is to replace the old AsyncAPI logo in this repo's README with the banner attached below that represents the new branding.

Here are a few guidelines for this change as well:

1. Make sure you are using Markdown syntax only
2. Be sure to remove the old logo as well as the old title of the repo as this image will replace both elements
3. Make sure you link this image to the website: https://www.asyncapi.com
4. If there is any description text below the repo title, let's make it left-aligned if it isn't already, so as to match the left-alignment of the content in the new banner image

Download the image file:
github-repobanner-diff.png.zip

---

Banner preview

Please note that this is only a preview of the image, the contributor should download and use the above zip file

[mcturco]

/gfi design

[github-actions]

Welcome to AsyncAPI. Thanks a lot for reporting your first issue. Please check out our contributors guide and the instructions about a basic recommended setup useful for opening a pull request.
Keep in mind there are also other channels you can use to interact with AsyncAPI community. For more details check out this issue.