chore: fix types for ESLint package builds (#10157)

### Description

Fixes builds of the `eslint-config-turbo` package that were failing on
type checking.

Author: anthonyshew

packages/eslint-config-turbo/src/flat/index.ts

@@ -11,4 +11,4 @@ export default [
       "turbo/no-undeclared-env-vars": "error",
     },
   },
-] satisfies Array<Linter.Config>;
+] satisfies Array<Linter.FlatConfig>;

packages/eslint-plugin-turbo/package.json

@@ -25,7 +25,7 @@
   ],
   "scripts": {
     "test": "jest",
-    "build": "tsup",
+    "build": "tsup && tsc --declaration",
     "check-types": "tsc --noEmit",
     "lint": "eslint lib/",
     "lint:prettier": "prettier -c . --cache --ignore-path=../../.prettierignore"