Add per-site READMEs describing what each site serves

Covers pages, data sources, config knobs, files and deploy target for
40k-rankings, aos-rankings, events, kingmaker and scouting. Also lists
events in the root README layout and points to the per-site docs.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

README.md

@@ -15,12 +15,16 @@ shared/
 scripts/
   render-header.mjs        # shared/header.template.html + sites/<site>/nav.html -> sites/<site>/public/header.html
 sites/
-  40k-rankings/
-  aos-rankings/
-  kingmaker/
-  scouting/
+  40k-rankings/          # 40K team leaderboard (ITC, LMC, Stat Check ELO)
+  aos-rankings/          # Age of Sigmar team leaderboard (ITC)
+  events/                # upcoming events across followed BCP circuits
+  kingmaker/             # Kingmaker league hub (Google Forms/Sheets)
+  scouting/              # BCP event roster scout + matchup matrix generator
 ```
 
+Each site has its own `README.md` describing what it serves, where its data
+comes from and what to edit.
+
 Each `sites/<name>/` is a full Vite project (own `package.json`, `vite.config.js`,
 `src/`, `index.html`). Two things are *not* duplicated per site: