Create a badge to download the generated notes

[tai271828]

We can now reserve the artifacts from CI and download them for accessing generated notes. However, the step to access the artifacts is not straightforward. It will be more handy if we can link the latest artifacts with a badge in the landing README.

More context, see this comment from issue #5 .

Possible solution:

• shields service provides customized badges. This note shows how to use shields.

[yungyuc]

It would be great if a link can be created for downloading the artifacts.