Make it possible to open DevTools unfocused

[sindresorhus]

Is your feature request related to a problem? Please describe.

During development, I open DevTools when the DOM is loaded with win.webContents.openDevTools({mode: 'undocked'});. The problem is that I don't want the DevTools window to be in the front of the app, so I would have to click the app window afterward to bring it to the front. I solved this with win.webContents.once('devtools-opened', () => win.focus());. The problem with this solution is that DevTools shows for half a second before the app window is brought to the front, which is quite jarring.

Describe the solution you'd like

I would like an option for .openDevTools() to specify it to open in the background and unfocused if the mode is undocked and if it's any other mode, it will just not focus DevTools.

win.webContents.openDevTools({
	mode: 'undocked',
	unfocused: true
});

---

Related: #4764 (comment)

We should probably change this behavior or add an option to not focus the devtools window.
- @zcbenz

[miniak]

@sindresorhus I've created a PR to address this issue #13852