The Package Manager only supports two file formats as package installation sources. Below are further explanations of those file formats.
The XML file is the main format used by the Package Manager as a way to store information about the package like its name, author, description, the path to the assets relative to the XML file itself, etc. On its own, an XML file doesn’t contain the actual assets themselves. Most of the time, the assets needs to be retrieved or downloaded separately and the XML file needs to be placed in the same directory where the assets are located.
A ZIP file is an archive containing the XML install file and the assets themselves. When installing a ZIP package, the package manager extracts the archive and locates the “install.xml” file under the root directory of the extracted archive. Once it has been located, the program parses it and proceeds with the installation. If the XML file could not be located, the package will be treated as corrupted and the installation process will be aborted.