Port homepage, posts section, shortcodes; update hugo.toml menus

- content/_index.md: homepage with site description and callout examples
- content/posts/asw-vocabulary.md: ASW data-* attribute vocabulary reference
- content/posts/getting-started.md: ASW-Hugo setup guide (updated URLs)
- hugo.toml: add params, taxonomies, menus (main + docs sidebar), ToC settings
- layouts/partials/nav.html: dynamic Hugo menu rendering (was hardcoded)
- layouts/shortcodes/callout.html, wikilink.html: ported from asw-hugo theme

Closes: asw#17, asw#13, asw#11, asw#16
28 pages build clean, deploy confirmed at port 8000.

layouts/partials/nav.html

@@ -1,7 +1,8 @@
 <nav>
   <ul><li><a href="/"><strong>{{ .Site.Title }}</strong></a></li></ul>
   <ul>
-    <li><a href="/docs/">Docs</a></li>
-    <li><a href="/examples/">Examples</a></li>
+    {{- range .Site.Menus.main }}
+    <li><a href="{{ .URL }}"{{ if $.IsMenuCurrent "main" . }} aria-current="page"{{ end }}>{{ .Name }}</a></li>
+    {{- end }}
   </ul>
 </nav>