RenderImage: Improve image render hook and lightbox integration

[Gasiyu]

This pull request introduces image processing and rendering across multiple configuration files and templates. The changes aim to improve responsiveness, optimize image quality, and provide fallback formats for better compatibility. It also refines the logic for handling featured images, post thumbnails, and lightbox functionality.

• Added new parameters in config.toml and docs/config.toml for responsive image sizes, resampling filters, fallback formats, and default image quality.

  [params.imgproc]
          enable = false
          # Default format for processed images
          format = "webp"
          # 0-100, image quality for compressed formats
          quality = 75
          # Image sizes for responsive images
          sizes = ["420", "789", "1019", "1430", "2048"]
          # Image resampling filter (Box, Lanczos, CatmullRom, MitchellNetravali, Linear, and NearestNeighbor)
          resamplingFilter = "Lanczos"
          # Default format for fallback images
          fallbackFormat = "jpg"
          # Default fallback image size
          fallbackSize = "789"

• Updated layouts/_default/_markup/render-image.html to include logic for responsive image sizes, fallback formats, and lazy loading.

• Enhanced layouts/_default/single.html to dynamically calculate image dimensions and generate responsive srcset attributes for featured images. Added support for lightbox integration.

• Modified layouts/partials/post-card.html to include responsive image handling for post card thumbnails.