docs: split Chart Types into one page per chart type

`components/charts/charttypes.adoc` documented 27 chart families on a
single 95 KB page, by a wide margin the largest article in the docs. Its
sections were already independent of one another, so readers had to
scroll past 17 chart types to reach Waterfall Charts, and consumers that
serve whole pages -- such as the documentation MCP server -- either
refused to load the page or truncated it from the top.

Split it into `components/charts/charttypes/`, one page per chart type,
with the former page becoming the section index. The index keeps the
`charts.charttypes` anchor and the alphabetical `ChartType` table, so its
URL and the links into it are unchanged; every section keeps its own
anchor on its new page.

Content is carried over verbatim apart from the adjustments the split
requires:

* Headings promoted one level; `example` headings put in title case.
* References that pointed at another section on the same page are now
  cross-page links, and the three sentences that read as "described
  previously" have been reworded.
* A note on Timeline Charts distinguishes the chart type from the chart
  timeline navigator, now that the two are separate pages.
* `&mult;` in the 3D article was a broken entity; it rendered literally.

`Sankey` is added to the accepted vocabulary and `OHLC` to the
abbreviation exceptions: both now appear in a page title, where they
can't be spelled out first.

Fixes #6003

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Author: peholmst

.github/styles/Vaadin/Abbr.yml

@@ -83,6 +83,7 @@ exceptions:
   - NAT
   - NGINX
   - OCR
+  - OHLC
   - OSHI
   - OSV
   - OWASP

.github/styles/config/vocabularies/Docs/accept.txt

@@ -196,6 +196,7 @@ Roboto
 [rR]esizable
 [rR]esync
 [rR]esynchronizations?
+Sankey
 Scala
 [sS]anitization
 [sS]cannability