Add back Mocha as a devdependency global to fix Intellisense (#5495)

Author: JustinGrote

package-lock.json

@@ -74,6 +74,7 @@
   },
   "optionalDependencies": {
     "@eslint/js": "^10.0.1",
+    "@types/mocha": "^10.0.10",
     "@types/mock-fs": "^4.13.4",
     "@types/node": "^22.19.17",
     "@types/semver": "^7.7.1",

package.json

@@ -10,7 +10,8 @@
     "verbatimModuleSyntax": true,
     "strict": true,
     "noEmit": true,
-    "module": "Preserve"
+    "module": "Preserve",
+    "types": ["mocha"]
   },
   "include": ["**/*.ts", "eslint.config.mjs", ".vscode-test.mjs"],
   "exclude": ["node_modules"]