Create CONTRIBUTING.md in meshery-linkerd repo

[leecalcote]

Issue Description
Create contributing.md that points to the central contributing.md in the Meshery repo.

Create a stub CONTRIBUTING.md in each of the repos that essentially say:
“You want to contribute to the project? Yay! We want you to! Visit our centralized instructions for contributing.", where the “contributing” is a hyperlink to the CONTRIBUTING.md in the main meshery repo.

Future Effort
In time, as more contributors join the project, we may need a meshery-community repo that has all this and much more info or to have a community / contributing section in the meshery docs.

[leecalcote]

Closed by PR #18