Mention `add_glyph`, `add_tools`, `add_layout`

[Sarah Bird]

I think it's good to mention the methods "add_glyph, add_tools, add_layout" which can be used on a chart, figure, or plot.

Mention in each briefly and then repetition will kick in? Or don't mention in charts as you're just getting going?

[Liz Dobbins]

These are covered extensively now in Tutorial 09 Models and Primitives. Close issue?

[Bryan Van de Ven]

thanks @eldobbins