Add an API Reference button under the Contact Support one leading to the product API documentation

[dmihaylo]

Based on internal discussions and efforts to improve the access to the API refs at all times, let's add an API Reference button to the right that will direct to the product API docs.

A possible location in the UI would be under the Contact Support one. Maybe we can think about having three same-styled buttons, the third being Improve This Article (or the new description Edit on GitHub: #259).