1.5.5: Allow `DocumentFragment` as the first parameter of `van.add`
This release allows DocumentFragment as the first parameter of van.add. Prior to this release, this should be already possible, but this release makes sure the DocumentFragment argument passes the TypeScript type-checking and sanity checks in van.debug.js.
There is no implementation change in van.js in this release.
See the release announcement: #290 (comment)