Is your feature request related to a problem? Please describe.
Add ability to add annotation to a chart with a line (vertical or horizontal), tooltip, and marker.

Describe the solution you'd like
User should be able to define an x or y value for the line, the marker, and the text to appear within the tooltip.

We can also expose a helper utility to the user to be able to generate the annotation configs for something like "get all the X positions for these data points matching these values".

Describe alternatives you've considered
This is one of three annotation-related tasks (see #81).

Additional context
Current feature in Kibana:

Kibana Cross Issues

Checklist

• this request is checked against already exist requests
• every related Kibana issue is listed under Kibana Cross Issues list
• kibana cross issue tag is associated to the issue if any kibana cross issue is present