Chart.js: [Documentation] Plugin API Hooks

[smcguinness]

The hardest thing I'm encountering while trying to write a plugin to modify a bar chart is to know what hooks I should be doing the changes in. For example, if I wanted to edit the value of the chart, I can do that in beforeUpdate, however I can't do that in afterDraw.

I'm sure there are even more nuances that I am missing in each individual hook beside just when the hook is called. It'd be a great help in that part of the documentation.

[etimberg]

@smcguinness good idea. I think we should create a flow chart of the create / update / render process to document where the hooks come in