Electron 镜像配置

解决 electron 和 electron-builder 的下载、构建速度慢的问题.

# electron 配置
export ELECTRON_MIRROR="https://npmmirror.com/mirrors/electron/"
 
# electron-builder 配置
export ELECTRON_BUILDER_BINARIES_MIRROR="https://npmmirror.com/mirrors/electron-builder-binaries/"