main.cjs to main.js in package.js

[cspence001]

Running npm start with the current version of package.js runs into an error when trying to locate the main.js file as it is set to look for main.cjs. Small fix.

Edit: Ref: https://github.com/ipfs-examples/js-ipfs-examples/blob/master/examples/run-in-electron/package.json

[pouriya73]

If you encounter an error, you can use this sign for addressing. #388
./
for example : ./main.cjs

[gmreburn]

#494 fixes this