Document targeted language version, minimum runtimes as required project configurations

[baywet]

This is eluded to in #30 and reported in https://github.com/microsoft/kiota/issues/3944

If we're documenting the required tooling in the getting started tutorials, it's generally higher than what it actually supported and incomplete.

We should have a separate page that documents:

• the target language version (e.g. 7.3 in dotnet)
• the minimum runtime (e.g. 4.6.2 in dotnet)
• the required project configurations.