AppImages that could benefit from AppStream metainfo

__Dear upstream author__, if you are reading this then chances are that someone has added a link to your application to the AppImageHub central directory of available AppImages, and has determined that your application could be represented better if we had more metadata about it, such as description, screenshots, etc.

This project, like many distributions such as Debian and Fedora, is using [AppStream metainfo files](https://www.freedesktop.org/software/appstream/docs/chap-Quickstart.html#sect-Quickstart-DesktopApps) for this. So it would be great if you could add an AppStream metainfo file to your AppImage, __make sure that it passes `appstreamcli` validation__, and then ping us, so that we can update the record for your application on AppImageHub. At the same time, doing so will bring your metadata into other distributions as well.

For __electron-builder__, see https://github.com/electron-userland/electron-builder/issues/1993