Fixes #2716

What's changed

• Now use app bar with actions moved to it
• Only 1 primary button per page
• Download moved to export page
• Documentation page now uses Jenkins styles and is not rendered separately
  • Now supports dark mode
• No longer reference external styles for documentation page
• Export warning has been turned down to info from warning and reworded
  • I haven't seen any export failures in ages and whilst a roundtrip of the whole config file may not work export is generally really good these days
• Minor changes to config export documentation
• Breadcrumbs applied consistently with matching content between page title, page heading and breadcrumbs

Screenshots

Configuration as code:

Export configuration:

Documentation:

For reference this is what the main config as code page (which has had the most changes) looked like before:

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