skpm publish does not add or update lastUpdated flag in plugin directory
After recently publishing a new Sketch [plugin](https://github.com/proteanstudio/sketch-palette-cleanser) (major and patch versions), I observed that no `lastUpdated` key is added to the object created in the [plugin directory file](https://github.com/sketchplugins/plugin-directory/blob/master/plugins.json). It appears as though items missing the `lastUpdated` key do not become visible on the [Sketch plugins](https://www.sketch.com/extensions/plugins/) page.

Please let me know if this assessment is incorrect or if I should seek to resolve this in another manner.  I observed that other recently added plugins are in a similar state and a newer plugin with a manually input `lastUpdated` date is appearing on the site.