lazy-load and auto-scale fixes

• added: automatic plan upgrade detection
• changed: better compatibility with other implementations of "native lazy load"
• updated: lazysizes.js to version 5.2
• fixed: custom domain for Easy IO prevents auto-scaling
• fixed: full-width background images auto-scaled due to scroll bars
• fixed: overrides for array-style exclusions not being applied

from 5.2.1:

• changed: WebP rewrite rules hidden for Cloudflare-protected sites
• fixed: Smart Re-optimize not working for PDF files
• fixed: Easy IO detects wrong domain when using separate domains for site and content