Add ISPG apps (ATMOSPEC)

[danielhollas]

TODO:

• [ ] Update title and description in the repo (I am assuming metadata are fetched automatically from setup.cfg?
• [ ] test registry build (not sure how this is done)

[yakutovicha]

• I am assuming metadata are fetched automatically from setup.cfg

yep 👍

[yakutovicha]

• test registry build (not sure how this is done)

ci/test builds the GitHub pages. In your case, it went without an error.

[unkcpz]

test registry build (not sure how this is done

You can also test locally by running the script bulid.sh and check by open the HTML in the browser.