Add a README.md and CONTRIBUTING.md guide.

[haacked]

What is this site for? How does one get it running locally? How does one contribute to it.

[haacked]

How is this site deployed?

[clairernovotny]

It has a CI build/deploy in Azure Pipelines. Merging to master should be all that's needed. Instance is here: https://dev.azure.com/dotnet/Membership

[haacked]

Ha! I meant that as a rhetorical question to be answered in the readme. But I should have been more clear about that. Thanks for answering!

[Rubix982]

But this still needs a READM.md, right?