doc: add & amend copyright headers

test/lint/lint_ignore_dirs.py

@@ -1,3 +1,9 @@
+#!/usr/bin/env python3
+#
+# Copyright (c) 2024-present The Bitcoin Core developers
+# Distributed under the MIT software license, see the accompanying
+# file COPYING or https://opensource.org/license/mit.
+
 SHARED_EXCLUDED_SUBTREES = ["src/leveldb/",
                  "src/crc32c/",
                  "src/secp256k1/",