iOS fastlane deliver metadata

I'm trying to configure deliver to send up my metadata for my app...

Following the screenshot here https://github.com/fastlane/fastlane/tree/master/deliver#readme

Specifically this one...

I have created my metadata folder...

However, when I first uploaded with fastlane deliver it didn't do several things.

It didn't add the app icon, it did add the marketing URL, the categories etc...

I added them manually myself on iTC and then today I've done another upload from fastlane deliver and it removed all that data again.

I have tried to find how to configure this stuff but the documentation is lacking (literally, this screenshot is all I have found).

For example... how should I upload the app icon? The content of the app_icon.txt file is ./fastlane/metadata/appicon.png. But I'm not sure where that path should be relative to?

The contents of the marketing_url.txt is http://thewebsite.com but that gets removed on each upload. But the copyright.txt works.

Is there somewhere I can see examples of what this data looks like?

The categories are also removed on each upload but I don't know what the text should be there? I have just got the name of the category (i.e. Health & Fitness) Is that wrong?

Any help or preferably a link to some docs would be very helpful.

The best way to get started with a correct metadata directory structure is to delete the metadata folder and the Deliverfile and run fastlane deliver init.

For the app icon, you'll have to provide a path to the file you want to use: https://github.com/fastlane/fastlane/blob/master/deliver/Deliverfile.md#app_icon