doc: Including docs references for addpsbtoutput where it seems to be missing

Author: s373nZ

mkdocs.yml

@@ -61,6 +61,7 @@ nav:
       - "Man Pages":
           # block_start manpages
           - "lightning-addgossip": "lightning-addgossip.7.md"
+          - "lightning-addpsbtoutput": "lightning-addpsbtoutput.7.md"
           - "lightning-autoclean-once": "lightning-autoclean-once.7.md"
           - "lightning-autoclean-status": "lightning-autoclean-status.7.md"
           - "lightning-batching": "lightning-batching.7.md"