Is your feature request related to a problem? Please describe.
Add ability to add annotation to a chart with text.

Describe the solution you'd like
User should be able to define an x, y starting coordinate for the text along with a way to customize text style.

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