Add SPDX 3.0 page (#71)

Author: bact

content/crosswalk/spdx-3-0.md

@@ -0,0 +1,19 @@
+---
+title: "Crosswalk for SPDX 3.0 SBOM"
+image: "/img/spdx.png"
+date: "2025-09-30"
+---
+
+The [System Package Data Exchange® (SPDX®)](https://spdx.dev/),
+formerly known as the *Software Package Data Exchange*,
+is a standard format for communicating information about components associated
+with systems.
+While traditionally known as "software bill of materials" or "SBOM,"
+SPDX 3.0 can describe datasets and be used in non-SBOM contexts.
+
+SPDX 3.0 supports the JSON-LD serialization format and often uses `.spdx.json`,
+`.spdx.jsonld`, `.spdx3.json`, or `.spdx3.jsonld` as the file extension.
+
+The crosswalk for the SPDX 3.0 fields is as follows:
+
+{{< crosswalk name="SPDX 3.0" >}}