Document how to use Visual Studio with GitLab
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### Description
From https://gitlab.slack.com/archives/C0NFPSFA8/p1501024891591663:
> most IDEs (like Visual Studio) have a vanilla Git plugin that will works with GitLab
We should document how to use Visual Studio with GitLab
### Proposal
### Links / references
* https://marketplace.visualstudio.com/items?itemName=MysticBoy.GitLabExtensionforVisualStudio
### Documentation blurb
#### Overview
What is it?
Why should someone use this feature?
What is the underlying (business) problem?
How do you use this feature?
#### Use cases
Who is this for? Provide one or more use cases.
### Feature checklist
Make sure these are completed before closing the issue,
with a link to the relevant commit.
- [ ] [Feature assurance](https://about.gitlab.com/handbook/product/#feature-assurance)
- [ ] Documentation
- [ ] Added to [features.yml](https://gitlab.com/gitlab-com/www-gitlab-com/blob/master/data/features.yml)
issue