Improve HTML rendering performance

Couple lines of CSS cut page loading and resize times
by 100 times (on my machine).

Description of what content-visibility is: https://web.dev/articles/content-visibility
Basically browser now doesn't render/layout invisible sections.
As a downside it makes scrollbar jump around slightly 
when you scroll the page, as browser recalculates the layout.

Section size was calculated using the following JS code:

const getAverage = (arr) => arr.reduce((p, c) => p + c, 0) / arr.length
getAverage(Array.from(document.querySelectorAll(".sect1").entries().map(([idx, el]) => el.getBoundingClientRect().height )))
getAverage(Array.from(document.querySelectorAll(".sect2").entries().map(([idx, el]) => el.getBoundingClientRect().height )))

config/khronos.css

@@ -730,3 +730,9 @@ li > p > a[id^="VUID-"].link { color: black; text-decoration: none; }
 li > p > a[id^="VUID-"].link:hover { color: black; }
 
 .vuid { color: #4d4d4d; font-family: monospace; }
+
+/* Improve page rendering performance */
+/* contain-intrinsic-size is the approximate average height of all sections */
+.sect1 { content-visibility: auto; contain-intrinsic-size: 98000px; }
+
+.sect2 { content-visibility: auto; contain-intrinsic-size: 13000px; }