Support git-lfs

[kieferrm]

Provide support for repositories that use git-lfs.

[joyceerhl]

The latest prerelease of GitHub Repositories on VS Code desktop supports reading LFS files from GitHub with the following setting (same goes for Azure Repos):

{
  "githubRepositories.experimental.lfs.read.enabled": true,
  "azureRepos.experimental.lfs.read.enabled": true
}

Caveats:

• No support on web yet due to CORS issues which need to be investigated
• No support for committing--needs further investigation
• No support for custom LFS server configuration in gitconfig
• Need to investigate support for Azure Repos
• Each file is retrieved with a separate request, we could improve performance and reduce network pressure by requesting multiple objects in a single request