feature #1318 Drop support of webpack-dev-server ^4.8, add support for webpack-dev-server ^5.0 (Kocal)

This PR was merged into the main branch.

Discussion
----------

Drop support of webpack-dev-server ^4.8, add support for webpack-dev-server ^5.0

Close #1290

Upgrade webpack-dev-server didn't have impact for Encore itself, but it can be the case for end-users.

After upgrading webpack-dev-server to ^5.0, my project that use the following devServer configuration is still working as expected:
```js
Encore.configureDevServerOptions((options) => {
    options.allowedHosts = 'all';
    options.client = {
        overlay: false, // hidden overlay: multiple errors caused by third-party scripts
    };
    options.server = {
        type: 'https',
        options: {
            pfx: path.join(process.env.HOME, '.symfony5/certs/default.p12'),
        },
    };
})
```

Commits
-------

c521591 Drop support of webpack-dev-server ^4.8, add support for webpack-dev-server ^5.0

Author: Kocal

Diff for: CHANGELOG.md

@@ -39,6 +39,39 @@ Encore.enableSassLoader((options) => {
 
 * #1324 Drop css-minimizer-webpack-plugin 5 support, only css-minimizer-webpack-plugin 7 is supported (@Kocal)
 
+* #1318 Drop webpack-dev-server 4 support, only webpack-dev-server 5 is supported (@Kocal)
+
+The dev-server options have changed between versions 4 and 5, see [the official migration guide to v5](https://github.com/webpack/webpack-dev-server/blob/master/migration-v5.md).
+For example:
+```js
+// With webpack-dev-server 4:
+Encore.configureDevServerOptions((options) => {
+   options.https = {
+     ca: "./path/to/server.pem",
+     pfx: "./path/to/server.pfx",
+     key: "./path/to/server.key",
+     cert: "./path/to/server.crt",
+     passphrase: "webpack-dev-server",
+     requestCert: true,
+   };
+});
+
+// With webpack-dev-server 5 (now):
+Encore.configureDevServerOptions((options) => {
+   options.server = {
+      type: 'https',
+      options: {
+         ca: "./path/to/server.pem",
+         pfx: "./path/to/server.pfx",
+         key: "./path/to/server.key",
+         cert: "./path/to/server.crt",
+         passphrase: "webpack-dev-server",
+         requestCert: true,
+      }
+   };
+});
+```
+
 ## 4.7.0
 
 ### Features

Diff for: package.json

@@ -42,7 +42,7 @@
     "tapable": "^2.2.1",
     "terser-webpack-plugin": "^5.3.0",
     "tmp": "^0.2.1",
-    "webpack-dev-server": "^4.8.0",
+    "webpack-dev-server": "^5.0.4",
     "yargs-parser": "^21.0.0"
   },
   "devDependencies": {