Modify HTTP request headers with Transform Rules

What this post added

Introduced HTTP Request Header Modification as a new action within Transform Rules, allowing administrators to set or remove HTTP request headers without writing code. This feature supports dynamic header values (e.g., bot score, country code), static values, and header removal. It also integrates with Cloudflare functions like `concat()` and `to_string()` for dynamic value construction. This provides an alternative to Cloudflare Workers for header manipulation.