Update name, link to documentation and description of PostNord API. 

Name changed form Sweden to PostNord due to PostNord is a service provider for Sweden and Denmark. 
Description adding Denmark.
Change linked documentation from from specific to general API entry point.

Update the link to the main page instead of the API directly

Meetup's REST API will stop working in winter 2021 and be replaced by their GraphQL API which is already active.

It seems like there is no free tier, according to their [pricing page](https://mysocialapp.io/pricing). 
Also, the project seems abandoned for the following reasons:
 - There haven't been any commits on their GitHub repos in a very long time (1+ years for most of them). [Link](https://github.com/orgs/MySocialApp/repositories)
 - The `Early Access` buttons show an expired Typeform. There is no other way to get access to the app.
 - Their documentation page links to the same expired Typeform in the first step of getting started. [Link](https://docs.mysocialapp.io/docs/setup)