Kibana: [TSVB] More detailed documentation

[alexfrancoeur]

As we begin to think about removing the time series visual builder experimental label, we will need to provide some more detailed documentation as to what functionality is available within this UI.

cc: @simianhacker @elastic/kibana-visualizations

[alexfrancoeur]

Based on conversations in the past few weeks, I'd like to make sure that when we update the documentation to include the following topics

• All functions definitions that are available in detail. I imagine most of these can link off to Elasticsearch documentation but we do have a few unique functions specific to TSVB. The Series Agg and upcoming Math function are only in TSVB. Our Calculation function is also an ES bucket script agg, which should be called out in the documentation
• The documentation should also explicitly call out that TSVB focuses on the most recent value / bucket

[renshuki]

Hi @alexfrancoeur, @simianhacker,

Sorry to bring back this over 1 year old issue but it looks like there is still no documentation for TSBV Math and Series Agg special aggregations. As TSVB is GA, I would like to know if there is some work in progress toward this. Thanks.