Add optional explain_score argument to Search Mode

[CShorten]

Usage Example:

qa.search(
  f"Similar podcasts to: {new_podcast_description}",
  limit=5,
  explain_score=True
)

This will populate the explain_score field in MetadataReturn.

[orca-security-eu]

Orca Security Scan Summary

Status	Check	Issues by priority
Passed	Infrastructure as Code	0   0   0   0	View in Orca
Passed	SAST	0   0   0   0	View in Orca
Passed	Secrets	0   0   0   0	View in Orca
Passed	Vulnerabilities	0   0   0   0	View in Orca