feature: sync extension versions

[JL710]

It would be cool if the versions of the extensions would be synced as well. I have an extension where I need a specific version. I have to pin that on each device by hand. It would be cool if the specific version or the latest status would be synced as well.

[daiyam]

The PR #103 is ready but it will need to wait until the bug I found in VSCode is fixed (I've made the PR microsoft/vscode#279630)