Open Plotly.js issue suggesting officially exposing internal plotly.js helpers

[bpostlethwaite]

It's hard to build a plotly.js app without relying on some helpers to assist querying axes, subplots and the like. The current ones are not stable as they are classified as internal methods.

Once the editor is almost complete let's document all of these helpers and make an issue in plotly.js that asks to have them officially exposed and "sealed" in a public API.