Electron Builder Wrong Icon File Name

### Issue Type

- [x] Bug Report
- [ ] Feature Request
- [ ] Support Question

## Description
When building a Cordova app for Electron on Linux, the icon file in `platforms/electron/build-res` has the improper name `installer.png`. ([The Linux configuration page](https://www.electron.build/configuration/linux#LinuxConfiguration-target) says `The icon filename must contain the size (e.g. 32x32.png) of the icon.`)
This is causing the icon file in the resulting package to be under `/usr/share/icons/hicolor/0x0`, and thus not showing correctly in the desktop environment. The name doesn't seem to change no matter what [attributes](https://cordova.apache.org/docs/en/latest/config_ref/images.html) I put on the `icon` element in the `` element in `config.xml`.

## Information

Building for Electron Linux x86_64 (any package type).

### Command or Code

`cordova build electron --release`

### Environment, Platform, Device

Building on Ubuntu 20.04.

### Version information

Plain Cordova CLI 10.0.0, no framework.

## Checklist

- [x] I searched for already existing GitHub issues about this
- [x] I updated all Cordova tooling to their most recent version
- [x] I included all the necessary information above

Start by reproducing `cordova build electron --release` on Ubuntu and inspect `platforms/electron/build-res/installer.png` and the generated Linux package. Trace how the Electron platform reads the `` icon in `config.xml`; done means the packaged icon uses a size-bearing filename and appears correctly in the desktop environment.

Written by the indexing model from the issue text.