feat(build): webpack@5 and webpack-dev-server@4 (#7826)

SwaggerUI is now built using `webpack@5`, with dev support for `webpack-dev-server@4`
- ES Module output bundle path now points to `swagger-ui-es-bundle-core`, which does not include dependencies
- No change to CommonJS output bundle or path
- Now uses Asset Modules, which replaces `file-loader`, `raw-loader`, and `url-loader`
- Removed unused rules/loaders for `.woff | .woff2 | .ttf | .eot` fonts and html
- Node polyfills are no longer bundled with `webpack@5`, and must be loaded separately and/or use `resolve.fallback`. 
As an example, SwaggerUI loads `process`, `buffer`, and `stream-browserify` as `devDependencies` in order to build development and production bundles.

SwaggerUI-React
- Now imports `swagger-ui-es-bundle-core`, and similarly outputs `swagger-ui-es-bundle-core` to its `dist` directory

Dev notes:
- Order of execution matters for the production npm build scripts. `build-stylesheets` needs to get built first, 
then cleanup of any empty artifacts, before building the various production bundles
- `Dev-helpers` now relies on `HTMLWebpackPlugin` to inject css and bundle files

flavors/swagger-ui-react/index.jsx

@@ -1,6 +1,6 @@
 import React from "react"
 import PropTypes from "prop-types"
-import swaggerUIConstructor, {presets} from "./swagger-ui"
+import swaggerUIConstructor, {presets} from "./swagger-ui-es-bundle-core"
 export default class SwaggerUI extends React.Component {
   constructor (props) {
     super(props)

flavors/swagger-ui-react/release/run.sh

@@ -9,10 +9,8 @@ cd "${0%/*}"
 mkdir -p ../dist
 
 # Copy UI's dist files to our directory
-cp ../../../dist/swagger-ui.js ../dist
-cp ../../../dist/swagger-ui.js.map ../dist
-cp ../../../dist/swagger-ui-es-bundle.js ../dist
-cp ../../../dist/swagger-ui-es-bundle.js.map ../dist
+cp ../../../dist/swagger-ui-es-bundle-core.js ../dist
+cp ../../../dist/swagger-ui-es-bundle-core.js.map ../dist
 cp ../../../dist/swagger-ui.css ../dist
 cp ../../../dist/swagger-ui.css.map ../dist
 

flavors/swagger-ui-react/release/template.json

@@ -28,6 +28,13 @@
   "name": "swagger-ui-react",
   "main": "commonjs.js",
   "module": "index.js",
+  "exports": {
+    "./swagger-ui.css": "./swagger-ui.css",
+    ".": {
+      "import": "./index.js",
+      "require": "./commonjs.js"
+    }
+  },
   "repository": "git@github.com:swagger-api/swagger-ui.git",
   "contributors": [
     "(in alphabetical order)",