Adding autocomplete / Intellisense from js file without importing it in vs code

Question

I have an JS sdk, which the users aren't using require to load it in their JS script. I'd like to offer intellisense / autocomplete of the SDK in VSCode, without requiring the user to do any difficult actions except installing an extension or setting something easy in jsconfig.

They have a js module with the SDK in a path other than the workspace. I've checked the following solutions:

1. snippets - but it doesn't support auto complete object properties
2. custom type definition - since it's not in the workspace. It doesn't load it (especially since the script is not doing a require or import statement)
3. Language server - seems over the top

Any suggestions?

---

Following this How to Import Intellisense files into vsCode (Visual Studio Code) , I've done the following:

1. added the following into my jsconfig.js but it didn't affect the autocomplete at all:

   "typeAcquisition": {
   "enable": true,
   "include": [
       "C:\\test.d.ts"
   ]
   

   }

2. Once I added /// <reference path="C:\test.d.ts" /> it was resolved

Is there a way to automate this using an extension? or avoid requiring the reference path at all?