In an Administrator command prompt (apprently not cmder), using absolute paths:
mklink /d <mallet path>\node_modules\mallet <mallet path>\dist\
ln -fs src/mallet node_modules/mallet
Install as a file dependency in package.json (one or both):
"mallet": "file:<path-to-mallet>",
"mallet-dev":<path-to-mallet>/dist