doc: highlight deprecated API in ToC

Highlight deprecated API methods/properties in "Table of Contents" for
increasing understandability. Adapted code to eslint standards.

PR-URL: https://github.com/nodejs/node/pull/7189
Fixes: https://github.com/nodejs/nodejs.org/issues/772


Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>
Reviewed-By: Roman Reiss <me@silverwind.io>
Reviewed-By: Sakthipriyan Vairamani <thechargingvolcano@gmail.com>