[Full Changelog](https://github.com/matrix-org/matrix-js-sdk/compare/v4.0.0-rc.1...v4.0.0) * Move & upgrade babel runtime into dependencies (like it wants) [\#1170](https://github.com/matrix-org/matrix-js-sdk/pull/1170) * Add a prepare script [\#1164](https://github.com/matrix-org/matrix-js-sdk/pull/1164)