feat(download): Add support for Github Enterprise

[ldoin]

This pull requests is related to #5447 and is aimed at adding support for Github Enterprise.

It's based on what has been done for private repositories hosted on github.com with #4254. A new attribute has been added to private hosts config for Accept header since it's not possible to set it like other headers.

I've successfully installed a tool available as a release in a Github Enterprise instance (https://github.company.com/owner/repo/releases/download/tag/XXXXXX_windows_amd64.zip) using the following config.

{
    "last_update":  "2023-03-28T15:12:26.6797756+02:00",
    "private_hosts":  [
                          {
                              "match":  "https://github.company.com/*",
                              "headers":  "Authorization=token ghp_XXXXXXXXXXXXXXXXXX",
                              "Accept":  "application/octet-stream"
                          }
                      ],
    "scoop_branch":  "master",
    "scoop_repo":  "https://github.com/ScoopInstaller/Scoop"
}

Checklist:

• I have read the Contributing Guide.
• I have ensured that I am targeting the develop branch.
• I have updated the documentation accordingly.
• I have updated the tests accordingly.
• I have added an entry in the CHANGELOG.

[ldoin]

If you have any questions, suggestions, or concerns regarding my pull request, I would be happy to discuss them and make any necessary changes.

Please let me know if I can / should do anything.

[rendevor]

I am not 100% sure, that pinning the existing approach for Github enterprise is a good approach.
I guess private repos and packages should be more flexible and support various platforms. Not only Github enterprise.