Update 01-interfaces.md (#4424)
Update 01-interfaces.md (#4424)

* Update 01-interfaces.md

* Update docs/concepts/01-interfaces.md

* Update docs/concepts/01-interfaces.md

* Update docs/concepts/01-interfaces.md

* Update docs/concepts/01-interfaces.md

Co-authored-by: Dylan Schiemann <dd378c4ca75f71f527acddef5b43fc35b68d5b7a@dojotoolkit.org>
ianstormtaylor/slate,ianstormtaylor/slate