This is command for packaging edge extension - manifoldjs -l debug -p edgeextension -f edgeextension -m \manifest.json. - I gave here the path of my extension manifest.json file.
After manifoldjs finished running following folders should create -
My Extension
edgeextension
generationInfo.json
manifest
AppXManifest.xml
Assets
Logo.png
Extension
manifest.json
popup.html
...
But in my case, folders are not creating and I am unable to package my extension.