docs: Add comprehensive store file format documentation #1831

Job	Run time
Test Release Process	4m 53s
Shellcheck	4s
Tests	1m 39s
Security Audits	13s
Lints	46s
goreleaser	0s
image-provenance	0s
binary-provenance	0s
verification-with-slsa-verifier	0s
verification-with-cosign	0s
	7m 35s

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