split from #16077

old website: https://checkstyle.sourceforge.io/version/10.21.1/

updates:

• left panel links/text is not wrapped dependency: bump org.apache.maven.plugins:maven-site-plugin from 3.12.1 to 3.21.0 #16077 (comment)
• header images is bigger than before and make redline is not touching top of page, details.
• tables headers text should aligned to top of cell, details.
• make line spacing for code snippets (line height) to be compact, as in was in old website
• code snippets have too much in top/bottom spacing details
• When sidebar becomes too large, it gets attached to the main content of the page: details
• remove spacing between top image and gray bar(with latest version and date) details
• Check description has different width , close to left panel and wihtout it. details
• reduce height of gap between left panel and top gray header details
• indention for code locks details
• panel that shows version and last datetime of release to be compact details.
• only in mobile mode, code block should be in 12px, in desktop mode, it should be same as other text. Requested at Issue #16300: Updated Move Syntax Highlighting to Site Generation Phase #16439 (comment)
• Non-formatted text are not wrapped. Details. Here is example https://checkstyle.org/checks/annotation/suppresswarningsholder.html#Example2-config