Add missing features for CaretPosition API (#7846)
Add missing features for CaretPosition API (#7846)

This PR is a part of a project to add missing interfaces and interface features to BCD that are from a spec in Editor's Draft or more and is supported in at least one browser.  This particular PR adds missing features, populating the results using data from the [mdn-bcd-collector](https://mdn-bcd-collector.appspot.com) project (v1.1.6), for the `CaretPosition` API.

Spec: https://drafts.csswg.org/cssom-view/#the-caretposition-interface

IDL: https://github.com/w3c/webref/blob/master/ed/idl/cssom-view.idl

Tests Used: https://mdn-bcd-collector.appspot.com/tests/api/CaretPosition
chrisdavidmills/browser-compat-data,mdn/browser-compat-data,chrisdavidmills/browser-compat-data,mdn/browser-compat-data