fix(deps): update node and electron

[adrienjoly]

Goals: improve security, fix #22.

Also fixes crash when quitting the app on macOS.

Changes:

• upgrade from node version 8 to 12
• upgrade from electron version 1 to 9 + latest version of associated dependencies
• move most dependencies to devDependencies (see https://github.com/electron/electron-packager/issues/827)
• only build x64 binaries (see https://www.electronjs.org/blog/linux-32bit-support)
• only build for darwin/macos, windows and linux
• re-format js files using latest version of standard