runtime(html): bump length of character references in syntax script (#15022)

This allows handling longer references such as
`&CounterClockwiseContourIntegral;`.

Signed-off-by: Mohamed Akram <mohd.akram@outlook.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/syntax/html.vim b/runtime/syntax/html.vim
index c975ae8..d067dde 100644
--- a/runtime/syntax/html.vim
+++ b/runtime/syntax/html.vim
@@ -191,7 +191,7 @@
 syn match   htmlArg contained "\<data-\h\%(\w\|[-.]\)*\%(\_s*=\)\@="
 
 " special characters
-syn match htmlSpecialChar "&#\=[0-9A-Za-z]\{1,8};"
+syn match htmlSpecialChar "&#\=[0-9A-Za-z]\{1,32};"
 
 " Comments (the real ones or the old netscape ones)
 if exists("html_wrong_comments")