Custom extensions do not work in VS Code in 2.x release.

[cabal95]

We use the custom extensions feature for our source files and with the 2.x release they are no longer working. I will be researching this more once I can work around #3928. At the moment I can't even get the extension to work with the volar start repo, which again might be a windows specific thing.

I will provide more specific reproduction steps if I can work around #3928 on my Linux machine.

[cabal95]

Thanks @johnsoncodehk for getting to this so quickly! I tested this fix on our main repo and it works like a charm.