[COMPLIANCE] Add Copyright and License Headers

Author: hashicorp-copywrite[bot]

scripts/build-sitemap.ts

@@ -1,3 +1,8 @@
+/**
+ * Copyright (c) HashiCorp, Inc.
+ * SPDX-License-Identifier: MPL-2.0
+ */
+
 import path from 'path'
 import { allDocsFields, allTutorialsFields } from 'lib/sitemap'
 import { unflatten } from 'flat'