chore: add kubecon na event to announcement banner - #6707

Changed pages include:

• index.html - view
• 404.html - view
• about-analytics-cookies/index.html - view
• blog/index.html - view
• community/index.html - view
• versioned/index.html - view
• about/case-studies/index.html - view
• about/testimonials/index.html - view
• community/contributing/index.html - view
• community/governance/index.html - view

There are more changes not included in the list