Merge branch '15-vc-schema' into 'main'

Default context for VC/VP to allow arbitrary JSON in credential subject

Closes #15

See merge request !15

internal/credential/credentials.go

@@ -12,6 +12,7 @@ import (
 var defaultContexts = []string{
 	"https://www.w3.org/2018/credentials/v1",
 	"https://w3id.org/security/suites/jws-2020/v1",
+	"https://schema.org",
 }
 
 type Credentials struct {