Schema 5.2 support

[hkong-mitre]

The new CVE Schema 5.2 adds support for PURLs. cve-core is used in the following applications and should be tested to verify correct behavior when Schema 5.2 CVEs are added to the ecosystem:

• jest tests
• bulk download
• web search
  • search ingest
  • OpenSearch mapping
• twitter update
• admin tools