perf: Improve website performance and Lighthouse score

[Dhiren-Mhatre]

Description

This PR improves the website's performance score from 42 to 50 by optimizing images and implementing lazy loading in the performance documentation section. These changes align with issue #115's goal of improving the website's usability and documentation readability.

Changes Made

• Optimized performance test images using lossless compression:
  • perf_network.png
  • fortio_performance_test.png
• Added lazy loading attributes to images in performance documentation
• Specified image dimensions to prevent layout shifts

Performance Improvements

• First Contentful Paint: Reduced from 4.4s
• Largest Contentful Paint: Reduced from 22.7s
• Total Blocking Time: Reduced from 590ms
• Overall Lighthouse Performance Score: Increased from 42 to 50

Testing Done

• Ran Lighthouse audits before and after changes
• Verified image quality remains clear and readable
• Tested lazy loading behavior
• Confirmed documentation readability is maintained

Related Issue

Part of #115 - Website redesign and implementation

• Addresses documentation readability improvement
• Contributes to better developer experience
• Improves website performance metrics

Screenshots

• Before:
  

• After:

• Even though the "Files Changed" section shows that the image dimensions have changed, the website still loads the images correctly due to its properties.
  
  

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[jayesh9747]

@Dhiren-Mhatre, I think Lighthouse performance depends more on your network speed, internet connection, and browser.

I got around 70% performance, but the results were not reliable. I also have a suggestion: use original images, and Hugo server will optimize them accordingly.

[Dhiren-Mhatre]

Thank you, @jayesh9747, for your valuable feedback. I'll revert manual image optimizations and let Hugo handle it. I'll keep the lazy loading attributes for performance benefits.