fix(demo): include all 15 cards in demo/README.md gallery (#6)

The hardcoded cards[] array in demo.yml still listed the original 9,
so the S-tier additions (heatmap, streak, by-year, weekday pair,
top-starred) were rendered into demo/<theme>/ but never referenced in
demo/README.md. Expand the array to the full 15 in README card-table
order.

.github/workflows/demo.yml

@@ -53,10 +53,16 @@ jobs:
             most-commit-language
             stats
             productive-time
+            productive-weekday
             contributions
+            contributions-heatmap
+            top-starred-repos
+            streak
             most-commit-language-all-time
             productive-time-all-time
+            productive-weekday-all-time
             contributions-all-time
+            contributions-by-year
           )
           themes=$(./ghstats -list-themes)
           {