You can get the code used for generating the docset via my Github.
Unfortunately, unlike the Maya one, I’ve elected not to include a full, ready-to-use version of the docset in this one due to the sheer size of the 3ds max documentation; the sources alone eclipse both 2016 and 2017 versions of the Maya docsets combined in terms of size. You’ll need to download the offline developer documentation for 3ds max from Autodesk’s official documentation website. Instructions for generating the docset are available in the repository’s README.md file.
Hopefully this helps out folks who are still stuck supporting 3ds max; I know firsthand how painful and slow searching through the official documentation can be. If you notice any bugs while using this, feel free to let me know and/or submit a pull request!