Add reference to Caliptra.

Author: bluegate010

specifications/device-trust-anchor-management/bibliography.yaml

@@ -0,0 +1,5 @@
+references:
+  - id: "caliptra"
+    title: "Caliptra"
+    publisher: "CHIPS Alliance"
+    url: "https://caliptra.io"

specifications/device-trust-anchor-management/spec.ocp

@@ -111,7 +111,7 @@ To mitigate the risk of a vendor's PKI becoming compromised, a device owner can
 
 ![Operator PKI anchor point](./diagrams/operator_anchor_point.drawio.svg){#fig:operator-anchor-point}
 
-Devices often support a hierarchy of identity keys, derived from a number of inputs. @fig:identity-key-derivation illustrates how identity keys are derived in Caliptra. Other devices may have different identity layering schemes.
+Devices often support a hierarchy of identity keys, derived from a number of inputs. @fig:identity-key-derivation illustrates how identity keys are derived in Caliptra [@{caliptra}]. Other devices may have different identity layering schemes.
 
 ![Identity key derivation](./diagrams/identity_key_derivation.drawio.svg){#fig:identity-key-derivation}