Implemented new campaign/session stable inputs and corresponding input source references

examples/campaigns/sample-campaign/campaign.yml

@@ -4,3 +4,5 @@ inputs:
   speakers_file: ./speakers.yml
   autocorrect_file: ./autocorrect.yml
   glossary_file: ./glossary.yml
+  players_file: ./players.yml
+  party_file: ./party.yml

examples/campaigns/sample-campaign/party.yml

@@ -0,0 +1,2 @@
+- name: Example Hero
+  type: pc

examples/campaigns/sample-campaign/players.yml

@@ -0,0 +1,2 @@
+- name: Example Player
+  role: player