From the Gravy dept.:
During the last few months, our team has been working hard to support extensions in Google Chrome's beta channel. Today, we are getting one step closer to this goal; developers can now upload their extensions to Google Chrome's extension gallery. We are making the upload flow available early to make sure that developers have the time to publish their extensions ahead of our full launch.

You can find all the info to write an extension in our docs. Once your extension is ready for the gallery, you'll need to upload a zip file of your code and an icon that helps users distinguish your extension. You'll also have the option to submit text, screenshots and/or YouTube videos that describe the functionality of your extension. All types of extensions are welcome in the gallery, provided they comply with our Terms of Service.

blog.chromium.org

chrome.google.com/extensions