Tweak final report title, and add subtitle

Author: dcoutts

doc/final-report/final-report.md

@@ -1,6 +1,7 @@
 ---
 title: "Storing the Cardano ledger state on disk:
-        final report for high-performance backend"
+        final report for a high-performance backend"
+subtitle: '[A technical report by Well-Typed LLP on behalf of Intersect MBO]{.smallcaps}'
 author:
   - Duncan Coutts
   - Joris Dral