Fix doc js initialization (#1736)
Fix doc js initialization (#1736)

1. Fix `collapsedSections is not defined` error.
PyTorch Sphinx theme seems to expect that `collapsedSections`
variable to be defined before its theme.js is executed.

2. Overwrite the link to GitHub project to torchtext
So that documentation link to torchtext's repository instead of
PyTorch core.
pytorch/text,pytorch/text,pytorch/text,pytorch/text