Bump webpack-dev-server from 4.9.3 to 5.2.1 in /miniPaint (#30)

Bumps [webpack-dev-server](https://github.com/webpack/webpack-dev-server) from 4.9.3 to 5.2.1.
- [Release notes](https://github.com/webpack/webpack-dev-server/releases)
- [Changelog](https://github.com/webpack/webpack-dev-server/blob/master/CHANGELOG.md)
- [Commits](https://github.com/webpack/webpack-dev-server/compare/v4.9.3...v5.2.1)

---
updated-dependencies:
- dependency-name: webpack-dev-server
  dependency-version: 5.2.1
  dependency-type: direct:development
...

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miniPaint/package.json

@@ -31,7 +31,7 @@
     "style-loader": "^2.0.0",
     "webpack": "^5.95.0",
     "webpack-cli": "^4.10.0",
-    "webpack-dev-server": "^4.3.1"
+    "webpack-dev-server": "^5.2.1"
   },
   "dependencies": {
     "@babel/runtime": "^7.14.5",