jpm does not work with this addon

[sedrubal]

I just started to learn about ff addons, and I don't know much. But somehow I can't run or debug this addon with jpm (1.0.4):

$ jpm run -b `which firefox`
JPM [info] Starting jpm run on Soundcloud Player
JPM [warning] The `version` entry must be specified, and it should follow semantic
versioning rules. For example, it must be a string containing three
values indicating major, minor, and patch versions. For example:

"1.4.56"
"0.0.1"
"1.0.0rc4"

http://semver.org

JPM [error] Error: The addon has no valid entry point. Either create an entry point
at `./index.js`, or set the `main` property to a valid path in
your addon.

Do you know, why this isn't working?