Images to add to the documentation

[welisheva22]

Here are some ideas, open to others:

1. On the core concepts page, add a picture that describes the concepts of fabric, peer, service, and access policy, ideally in the same image (a pictorial representation of how they relate to each other). Perhaps define each term with a short definition in the image.

2. On the contribution guidelines page, same thing. A picture to define the terms Hugo, Docsy, Netlify and Github, as well as how they relate to one another. The image may include short text to define each term.

3. In the iPerf3 tutorial, a picture including the client and server clusters and how ClusterLink links them together. Include a depiction of import, export, and policy in the diagram if possible.

4. On the deployment operator task page, add an image to illustrate the purpose of this step and what it does for the system.