Snapcraft 2.5 comes with a kernel and kbuild plugin as Ubuntu developers work on being able to snap a kernel, the kernel snaps are considered experimental in this version. Snapcraft 2.5 also has support for downloading snaps and other enhancements.
More details on Snapcraft 2.5 can be found via the release announcement. There is also this new blog post about using the new kbuild and kernel plugins of Snapcraft 2.5.
If this is somehow your first time hearing of Ubuntu's Snappy, learn more about the innovative packaging tech via developer.ubuntu.com.