Advance RFC #0776 `"Author Built-In Blueprints in TypeScript"` to Stage Recommended #520

Job	Run time
Does PR add RFCs?	11s
Verify Accepted PR URL is correct	16s
Filename matches RFC number	15s
Stage must be 'Exploring' (via label) for new RFC before merging	2s
Frontmatter stage must be 'accepted' before merging	13s
Only one RFC can be added in a PR	1s
RFC must be in only one stage before merging (labels)	1s
	59s

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