Add support for downloading Windows DLLs from Bitbucket

[mbabker]

"Promoting" #110 (comment) up to its own feature request as that thread seems more focused on Private Packagist (or other Packagist-like repos) than this one.

I was going to open a feature request for the event extension to add support for PIE, but as they use Bitbucket, they wouldn't be able to add Windows support at this time.

[asgrim]

Thanks @mbabker - I'll treat this as a specific ask for Bitbucket support; we can add this, I'd rather add support for specific repo providers if/when they come up, rather than just trying to support "everything" (e.g. lets say we add Gitlab support, but then no-one uses it, it's kinda waste of time heh).

[macintoshplus]

@mbabker your request is like mine. I mean Private Packagist for simplicity ;-)