Support for markdown has also been added, which was referenced in issue #7 by @Haroenv. I haven't found a markdown grammer file that highlights liquid syntax.
If you want to have snippets suggestions as you type, you'll need to add the below to your global settings or workspace settings:
Alternatively, you can also use the keyboard trigger ctrl+ space
Support for html has been added, due to some odd behavior from other extenions I use which doesn't provide support for liquid file extension.
Roadmap & Contributing
I do have plans to continue adding more snippets, based on the Jekyll Tips Cheat Sheet, but PLEASE feel free to contribute and/or file issues with requests. If you do want to contribute please make sure to create a feature branch and when creating a pull request to rebase or squash prior to.