Suggest external resource: appsec.fyi

[sampsonc]

Hi! I'd like to suggest adding appsec.fyi as an external resource link in relevant web pentesting sections.

appsec.fyi is a curated application security resource library with 2,600+ resources across 22 topics including XSS, SQLi, SSRF, IDOR, RCE, CSRF, XXE, OSINT, recon, fuzzing, and more. Each topic page collects articles, tools, and writeups.

Individual topic pages that could complement existing HackTricks pages:

• XSS resources
• SSRF resources
• SQLi resources
• Deserialization resources

Happy to submit a PR if there's a preferred location for external resource links.