feat(tool): fix failing tests

Author: JigyasuRajput

test/test_vex_validate.py

@@ -300,6 +300,7 @@ def test_network_timeout(self, mock_load_local, mock_urlopen):
             "@context": "https://openvex.dev/ns/v0.2.0",
             "@id": "test-vex",
             "author": "test",
+            "timestamp": "2025-01-01T00:00:00Z",
             "version": 1,
             "statements": [],
         }
@@ -325,6 +326,7 @@ def test_network_connection_error(self, mock_load_local, mock_urlopen):
             "@context": "https://openvex.dev/ns/v0.2.0",
             "@id": "test-vex",
             "author": "test",
+            "timestamp": "2025-01-01T00:00:00Z",
             "version": 1,
             "statements": [],
         }
@@ -388,6 +390,8 @@ def test_utf8_encoding_handling(self):
             "@context": "https://openvex.dev/ns/v0.2.0",
             "@id": "test-vex-üñíçødé",  # Non-ASCII characters
             "author": "Test Authör",
+            "timestamp": "2025-01-01T00:00:00Z",
+            "version": 1,
             "statements": [
                 {
                     "vulnerability": {"name": "CVE-2024-0001"},