Extensions fail to load in subprocess which generates docs

[vdayanand]

We try loading the package in a new "isolated" environment:

DocumentationGenerator.jl/src/DocumentationGenerator.jl

Line 36 in 61b0dea

@eval(Main, (using $pkg_sym; $pkg_sym))

.

Julia seems to lookup extensions in environment but the package it belongs to in memory (which is loaded as part of DocumentationGenerator). So the fix/workaround would be to no longer use a isolated environment instead reuse the DocumentationGenerator's environment