Add GitSmart extension

[arielpollack]

• I have read the note above about PRs contributing or fixing extensions
• I have tried reaching out to the extension maintainers about publishing this extension to Open VSX (if not, please create an issue in the extension's repo using this template).
• This extension has an OSI-approved OSS license (we don't accept proprietary extensions in this repository)

Description

This PR introduces GitSmart extension.
I'm the author and currently it's easier for me to auto-publish this extension rather than publishing to both marketplaces.
When I'll set up continuous deployment in my repo I'll remove if from auto publish.