Articles/issue 104 heartbeats and custom checks nsb3

Added the v3 plugins. Related to https://github.com/Particular/docs.particular.net/pull/373 and #104 

@indualagarsamy can you double check if all the links to MyGet are correct?

@dannycohen I think we should merge this as is and as soon as we have stable plugins update the article to point to NuGet