Expose Electron builder configuration properties via capacitor.config.json and change build process to read them dynamically

[coreyjv]

In doing some testing on deep linking in #36 I realized that the built app was pulling statically defined properties from the electron/package.json which is mentioned in the Quick Setup guide for Electron Builder.

I would like to see these values pulled dynamically from the capacitor.config.json at the root of the project.

So the mapping would be as follows:

Capacitor Property	Electron Builder Property
appId	appId
appName	productName

There's likely additional properties we'd want to expose as well like Electron Builder's mac.category.

Finally I believe for deep linking to work for built application it has to be statically defined per the discussion here: electron-userland/electron-builder#1552 so I think it's worth exposing the custom protocol or scheme in the configuration and not have to modify the electron.index.ts to set it.

[IT-MikeS]

Yep most static configuration options will be in the capacitor.config come version 3 of capacitor. See ionic-team/capacitor#3141

Like the Android and iOS platforms of Capacitor, Electron will still follow the idea of not getting in the way of the normal development of that platform. So if a process is done one way in electron apps without capacitor, I don't want to make it different in the capacitor platform.

[IT-MikeS]

This will be in v3

[coreyjv]

@IT-MikeS -- What does the solution for this look like? I wouldn't mind contributing to the feature but would like to understand what you're looking for.

Thanks!