Chrome extension google docs api get request, how to get cursor location?

I am making a chrome extension that does some google docs text insertion. I need to find the cursor location. using:

https://developers.google.com/docs/api/reference/rest/v1/documents/get

I get the document data back, but the cursor location is not included. Google apps scripts seems to be able to retrieve it (see https://developers.google.com/apps-script/reference/document/position).

But I don’t want to use Googla apps scripts unless I have to (some have said extensions and google apps scripts don’t mix well).

How do I get the cursor location using API calls for google docs?