Code snippets for .cake files are provided by the VS Code Cake Extension.
Full details on how to install an extension for VS Code can be found here
Intellisense support for .cake files is provided through the Omnisharp project, along with Cake.Bakery. Full details can be found in the release blog post.
There is a playlist of videos showing off the new features in each release of the Visual Studio Code Extension for Cake here: