Change log for MANDIANT_CUSTOM_IOC

Date Changes
2023-12-19 - Mapped threat.threat_feed_name to Mandiant.
2023-12-07 - Mapped first_seen to metadata.interval.start_time.
- When type is fqdn/ipv4/url, then mapped custom_ioc_expire_date to metadata.interval.end_time.
- Mapped threat_rating.threat_score to entity.entity.labels.
- Mapped threat_rating.severity_level to threat.severity.
- Mapped threat_rating.confidence_level to threat.confidence.
- Mapped verdict_simple.timestamp to verdict_info.verdict_time.
- When verdict_simple.verdict is malicious, then set verdict_info.verdict_response to MALICIOUS.
- Mapped verdict_info.verdict_type based on verdict_simple.verdict_source.
- Mapped category to threat.category_details.
- Mapped threat_rating.confidence_score to threat.confidence_details.
- Mapped threat_rating.threat_score to threat.risk_score.
2023-11-17 Newly created parser.