[Proposal] Support self-hosted GitHub

[gerich-home]

Hi, a good improvement for your awesome extension could be a configuration that allows you to configure base URL of your github instance.

So when your github instance is not publicly accessible and is located in the URL like that:
https://github.my-company.com/my-org/my-repo/
the extension should still be able to create a link.

Here is a piece of code that needs to be changed: https://github.com/gimenete/github-linker/blob/master/src/extension.ts#L11-L22
And this and this is an example of how to support options to be specified in settings.json file

[kodai-shirafuta-skl]

nice! @gimenete please! this is great extension and I need it at our office.

[rbxmdavis]

Yes please!
@morganwu277 has already forked and made the necessary changes here:
morganwu277@394aac5

It would be awesome if this functionality were incorporated back upstream into this codebase so that it is available for everyone in the VSCode Extensions Marketplace.

[riendeau]

@gimenete Are there any prospects for getting this support included in a release? There are a couple PRs (#10, #11) out there which address this - can one be merged? I've been using the release from @rbxmdavis's fork for a while now, but it would be great to have this functionality in the extension proper. Thanks!