It's available as a Nuget package or via the Umbraco backoffice installer:
https://github.com/KOBENDigital/bento.editor
https://our.umbraco.com/packages/backoffice-extensions/bento-editor/
Very proud to have been involved in it's development - the editor takes advantage of all the infinite editing goodness in v8, solves the problem of element based and reusable content blocks, offers multiple layouts and cell based grid designs in a single block... and its blisteringly fast too.
Give it an install and let us know what you think?