Add devtron in development mode

[JanMalch]

This PR adds the devtron extension in development mode.

[sindresorhus]

electron-debug already adds it if you add Devtron as a dev dependency: https://github.com/sindresorhus/electron-debug#activates-devtools-extensions However, that doesn't seem to work when nodeIntegration is off. I think it would be better to fix that in electron-debug first.

[JanMalch]

Ah, I didn't see that, my bad.
I can look into electron-debug.

[JanMalch]

I added a preload.js to electron-debug (JanMalch/electron-debug@e2f4a56), which can be imported in the boilerplate's preload.js.

If this is a good solution I can extend the README accordingly.

[sindresorhus]

I was thinking reducing the boilerplate even more by taking advantage of https://electronjs.org/docs/api/session#sessetpreloadspreloads in electron-debug.

[reZach]

@JanMalch, I've had no success in turning on Devtron in development branches in my personal projects, have you got Devtron working? A handful of people seem to think the project is already dead.

[sindresorhus]

How can we move this pull request forward?

[JanMalch]

I also got the impression that it's dead and in the end I didn't use it either. I can take a look at it again in the next few days.

[sindresorhus]

Bump