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.
But eventually this is where we will have the documentation. Anyway, it's not that important. We can change that link once it's there - we should just make sure we don't forget. Tie a note to your finger.