IACO-527: GitHub documentation

It would probably be best to read the documentation instead of looking at the markdown, so feel free to open up the following links:
https://github.com/yuval-netanel/inapp-ios/tree/IACO-527-github-documentation
https://github.com/yuval-netanel/inapp-ios/blob/IACO-527-github-documentation/doc/integration.md

As a semi-outsider, you should definitely give this a glance, @rauchy.
Yes - maybe a one liner as an intro:
"Klarna In-App allows you to offer Klarna's payment solution for on demand services sold in a mobile app. For example: app selling concert tickets, taxi rides, food pick-up, etc."
Guy, you can fix the phrasing as you like.
Once done, I'll send the whole Github documentation to Charlotta from communications.