mdattachment package
This package allows to drop image files into markdown documents. The file is copied into a directory and the corresponding link is added into the document.
Configurable options
The output directory can be configured to be a folder with the same name of the markdown file (without extension), or a common folder for all files of the files in one directory.
A checkbox allows to chose if the dropped file have to be copied into its destination folder or if it can be moved therein.
Disclaimer
This is my first atom package. Use it at your own risk.