Remove archived plugin

The plugin at https://github.com/GoogleChrome/preload-webpack-plugin is in archive-only mode and is implemented by the (maintained) https://github.com/jantimon/resource-hints-webpack-plugin or https://github.com/principalstudio/html-webpack-inject-preload

README.md

@@ -79,7 +79,6 @@ The `html-webpack-plugin` provides [hooks](https://github.com/jantimon/html-webp
  * [html-webpack-include-assets-plugin](https://github.com/jharris4/html-webpack-include-assets-plugin) for including lists of js or css file paths (such as those copied by the copy-webpack-plugin).
  * [html-webpack-injector](https://github.com/thearchitgarg/html-webpack-injector) to inject chunks in `head` or `body` (different locations ) of same html document.
  * [resource-hints-webpack-plugin](https://github.com/jantimon/resource-hints-webpack-plugin) to add resource hints for faster initial page loads using `<link rel='preload'>` and `<link rel='prefetch'>`
- * [preload-webpack-plugin](https://github.com/GoogleChrome/preload-webpack-plugin) for automatically wiring up asynchronous (and other types) of JavaScript chunks using `<link rel='preload'>` helping with lazy-loading
  * [link-media-html-webpack-plugin](https://github.com/yaycmyk/link-media-html-webpack-plugin) allows for injected stylesheet `<link />` tags to have their media attribute set automatically; useful for providing specific desktop/mobile/print etc. stylesheets that the browser will conditionally download
  * [html-webpack-inline-style-plugin](https://github.com/djaax/html-webpack-inline-style-plugin) for inlining styles to HTML elements using [juice](https://github.com/Automattic/juice). Useful for email generation automatisation.
  * [html-webpack-exclude-empty-assets-plugin](https://github.com/KnisterPeter/html-webpack-exclude-empty-assets-plugin) removes empty assets from being added to the html. This fixes some problems with extract-text-plugin with webpack 4.