Providing context in your reports and dashboards is a key part of any good analysis and I love annotations for that purpose.
Annotations are not supported out of the box in Data Studio so I decided to roll up my sleeves and learn about community visualizations and D3. I adapted the wonderful d3-annotation package for use with Data Studio and this what I came up with:
To use this in your own reports please check out this data studio report for instructions.
Source code is available on github.