reacthtmlpack/src/entry/index.js

Added the missing piece of treating `index.html` as entry point in webpack bundles.

export { default as WebpackNullEntry } from "./WebpackNullEntry";
export { default as WebpackScriptEntry } from "./WebpackScriptEntry";
export { default as WebpackStyleEntry } from "./WebpackStyleEntry";
export { default as ReactRenderToStringEntry } from "./ReactRenderToStringEntry";