Consider exposing QueryGitLabAPI or some equivalent

[RamblingCookieMonster]

1. Provide a general summary of the issue in the Title above

So! If an endpoint isn't included here, it would be handy for us to borrow your scaffolding for handling pagination, and other API basics for new endpoints. For example, you have a command for getting a project tree - I'd like to get content of particular items (any readme.md) via https://docs.gitlab.com/ce/api/repository_files.html. I could write my own wrapper for this, but if I could have a generic Invoke-GitlabAPI -Method Get or some such command, it would be super helpful and let me just use your module for most things.

I'm not sure if other GitLab APIs behave the same, so maybe this isn't possible. Just a hope : )

2. Describe Your Environment

Operating System and PowerShell version: Any

3. Expected Behavior

[comment] If you're describing a bug, tell us what should happen
[comment] If you're suggesting a change/improvement, tell us how it should work

Invoke-GitlabAPI -Method Get -Parameters $SomeHashParameters -Path "projects/$ProjectID/repository/files/$SomeFilePath"

This would require a little rework - ideally a public version of QueryGitLabAPI would split out components into the relative uri ($path above) and endpoint parameters ($parameters above)

6. Context

[Comment] How has this issue affected you? What are you trying to accomplish?

Nothing super exciting. I'm creating an overlay of our various documentation spots, and want to basically loop through every project, and for each, find every readme.md, so that any searches include our various documentation spots, including gitlab / source control!

Cheers!