chore: updated blog assets and optimized images

[hakantapanyigit]

Why are these changes needed?

Optimized blog assets by replacing PNG images with .webp format for improved performance and reduced file size. Updated blog content for consistency and better readability.

Related issue number

N/A

Checks

• I've included any doc changes needed for https://docs.ag2.ai/. See https://docs.ag2.ai/docs/contributor-guide/documentation to build and test documentation locally.
• I've added tests (if relevant) corresponding to the changes introduced in this PR.
• I've made sure all auto checks have passed.

[qingyun-wu]

Thanks!