The HTML Campaign Upload connector make it possible for digital agencies to create HTML based campaigns in their own tool suites. When ready they can package all campaign assets (HTML, CSS,JS, images etc) into a ZIP and upload it into SDL Web. The benefit of this extension is that digital agencies are given the freedom (within some defined boundaries of the brand guidelines, used CSS framework etc) to build campaign content with unique layout and interaction elements. And that without the need of creating specific templates in SDL Web for the created campaign.
For more info please refer to: https://github.com/sdl/dxa-flexible-campaign-content
See README.md in the ZIP for installation instructions.