message: add angular plugin deprecated message
diff: +> Note: Angular Plugin is moved to its own repo [here](https://github.com/microsoft/applicationinsights-angularplugin-js). This Plugin is deprecated. Please refer to the new repo for usage instructions, and open issue there.
  # Microsoft Application Insights JavaScript SDK - Angular Plugin
  [![Build Status](https://travis-ci.org/microsoft/ApplicationInsights-JS.svg?branch=master)](https://travis-ci.org/microsoft/ApplicationInsights-JS)
  