Include whitelisted HTTP headers in the `extended_unique_key` computation

[vdusek]

• Modify the extended_unique_key computation to include a set of predefined HTTP headers, alongside the existing normalized URL and payload.
• Only include headers from the whitelist.
• Identify which headers should be included, such as Accept, Accept-Language, Authorization, and others that may affect request outcomes.
• See the issue #178 for further context.

[ravi-hash]

Hey will you assign this issue to me

[vdusek]

Hi @ravi-hash, sure, thanks for your interest in Crawlee.