Add support for More SCM releases

[Kamsiy]

Description
Currently the only supported source code management tool is the public GitHub endpoint.

version/upgrade/github/head_fetch.go

Line 14 in c6a7640

const gitHubLatestReleaseURLFormat = "https://github.com/%s/releases/latest"

This proposal is to support upgrade notice for New Releases on GitHub enterprise, public Gitlab and GitLab Enterprise

Reasons
This would expand support to Gitlab & Github enterprise projects

[mszostok]

Hi @Kamsiy

That makes sens to me 👍

The only restriction would be that also the GitHub enterprise repository needs to be publically available 🤔 not sure if this is a common scenario.

[Kamsiy]

if its Github/Gitlab enterprise, it would be an internal & private release

[Kamsiy]

This means, if its on GitHub/Gitlab enterprise or a private repo, the version package would need a GitHub token to access the release (assuming the user has permission to that repo).

goreleaser has a similar customization for releasing projects on Github Enterprise. https://goreleaser.com/scm/github/?h=github#github-enterprise