Ability to specify binary mirror

[ConfuddledPenguin]

During the postinstall of this module it attempts to download the source code and build this locally.

In certian coorporate, regulated and/or security conscious firms external downloads are not tolerated meaning that this package can not be used within them.

To work around this I suggest allowing the user to specify an enviroment variable which points to a download location. Where downloading from the internet is not an option, the user can set this header and the binary can then be downloaded from an internal location once cleared for use.

This is a similar pattern as to what is used by puppeteer, electron and cypress

[ConfuddledPenguin]

I should have had a deeper look before I created a PR. I noticed that this issue has already been raised and a PR #90 has been created a declined for this issue.

In the response to the linked PR it was suggested that this should be an update in bin-wrapper instead of this module.

But like the commenters in that PR I struggle to see how that would look for projects like this that create a paramterised version of the url the the version, unless it is ignored and the user is required to ensure they change this when upgrading.