Explore support for SPDX 3.x validation and conformance with JSON-LD

As it appears official JSON schema support (via serialization) has been abandoned we must look to see what we can do with JSON-LD and limited support for it in Golang...

**References**:
- _A.1 Differences between V3.0 and V2.3_ : https://github.com/spdx/using/blob/main/docs/diffs-from-previous-editions.md/
- "hello world" example: https://github.com/spdx/spdx-spec/blob/support/3.0/examples/jsonld/package_sbom.json
- Use as a starting point (testcase)

See: https://github.com/piprate/json-gold/

e.g.,
```
import (
"fmt"
"github.com/piprate/json-gold/ld"
)

func processAndValidateJSONLD(jsonData string) error {
proc := ld.NewJsonLdProcessor()
options := ld.NewJsonLdOptions()
// Set the processing mode to the latest spec (e.g., "json-ld-1.1")
options.ProcessingMode = "json-ld-1.1"

// The Expand function will return an error if the JSON-LD is invalid
expandedDoc, err := proc.Expand("https://example.com/some-base-url", jsonData, options)
if err != nil {
return fmt.Errorf("JSON-LD validation error: %w", err)
}

fmt.Printf("JSON-LD document successfully processed (expanded), contains %d top-level elements.\n", len(expandedDoc.([]interface{})))
return nil
}

func main() {
doc := `{
"@context": "
```