* Add webpack-dev-server (for hot module replacement) to serve statics, add HardSourceWebpackPlugin to improve re-compiling speed

* Serve statics using webpack-dev-server instead of lens-proxy, redirect request of Lens.html/Lens.js to webpack-dev-server

* Add react-refresh-webpack-plugin and its dep for hot-reload

* Add hot-reload plugin, and make proxy redirects requests to webpackdevserver

* Add hard-source webpack plugin to main process

* Remove parameter 'path' of handleStaticFile

* Upgarde webpack to v4 latest stable

* Fix build error: plugins shouldnt be null
Signed-off-by: Hung-Han (Henry) Chen <1474479+chenhunghan@users.noreply.github.com>