Update dependency html-webpack-plugin to v4.0.0-beta.8 (#40)

Author: renovate[bot]

package-lock.json

@@ -58,7 +58,7 @@
     "eslint-plugin-react-hooks": "1.7.0",
     "file-loader": "3.0.1",
     "fs-extra": "7.0.1",
-    "html-webpack-plugin": "4.0.0-beta.5",
+    "html-webpack-plugin": "4.0.0-beta.8",
     "identity-obj-proxy": "3.0.0",
     "is-wsl": "1.1.0",
     "jest": "24.9.0",