Add meshery docker extension

[YashKamboj]

Current Behavior

Meshery docker extension is missing from the list

Desired Situation

Add meshery docker extension on [layer5.io/projects](https://layer5.io/projects)

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[Nikhil-Ladha]

But, it is a part of Meshery itself. Not a separate project 🤔

[YashKamboj]

@Nikhil-Ladha @leecalcote told me to do it

[leecalcote]

@Nikhil-Ladha has a good point. I had wondered this myself, but figured that we would list it as some of the other projects are also sub-projects (e.g. SMI Conformance, Service Mesh Patterns ) like the Docker Extension is. I figure that we might as well toot our own horn and that we should point people to this easy deployment method of Meshery when we can. What do you guys think?