Use of official images for blogs

This information can be found by searching for the given companies brand guidelines (they also have other names). Here are the brand guidelines that you wanted:

1. DotNet - github.com/dotnet/brand
2. Docker - docker.com/legal/trademark-guidelines
3. Angular - angular.io/presskit

I usually just search "[foo] brand guidelines" and it will usually come up with a page or pdf for that company's guidelines.