docs: add standalone Code of Conduct doc where GH can see it

[mboersma]

Reason for Change:
Adds the Microsoft Open Source Code of Conduct as a standalone document in the project root, as expected by GitHub community standards.

Issue Fixed:
None, but see also Azure/aks-engine#510

Notes for Reviewers:

[kkmsft]

@mboersma - is there a way for us to add a link to this and place that link as separate file as requirement ?

[kkmsft]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[mboersma]

@kkmsft the trick is that Microsoft requires us to have the final paragraph of the README link to our online Code of Conduct, but GitHub wants to see a standalone Markdown document.

So the requirements don't sync up perfectly, but I'll add a link in the README to the local version as well.

[mboersma]

Or did you mean having CODE_OF_CONDUCT.md just contain a link to the online version? I thought of that and it would ensure we don't repeat ourselves. But I'm guessing that GitHub's intent is to have the project be self-documenting so that a tarball download contained this info.

The simplest solution seemed to be to allow ourselves to repeat the document, but let me know what you'd prefer.

[kkmsft]

@mboersma - First Thank you :-) for looking at this and providing the context. I am leaning towards the first choice you mention above - CODE_OF_CONDUCT.md just contain a link to the online version. Would prefer that it's a consistent pointer and not repeat ourselves.

[kkmsft]

Thank you, @mboersma