[meta] Improve contributor experience

[jnv]

I would like to suggest the following improvements to help possible contributors:

• Currently the Issues flow is a generic one offering only possibility to submit a bug or question, we could:
  • Improve the Bug template to better capture bugs with existing capabilities through explicit questions in this area (i.e. "What capability is affected?" "What provider you use?") and also provide explicit instructions on capturing debugging information
  • Open Discussions for this repository to capture capabilities / providers requests.
  • Add specific options to "Request new capability" and "Request new vendor" guiding the user to Discussions
• Streamline the Contribution guidelines
  • Currently it's mostly a generic guide with only a few some repo-specific suggestions and it's easy to miss some important things like Conventions
  • For example we don't explain anywhere how to do testing (and that you probably shouldn't run all the tests since you don't have all the necessary keys)
  • It might be helpful also to explain in better detail what kinds of contributions are welcome and where to look for requested capabilities / providers.
• Why we do have Changelog here?

[jnv]

We could use DefinitelyTyped for inspiration.