Add httpx-secure to third party packages (#3629)

Co-authored-by: Kim Christie <tom@tomchristie.com>

Author: Zaczero

docs/third_party_packages.md

@@ -24,6 +24,12 @@ Provides authentication classes to be used with HTTPX's [authentication paramete
 
 This package adds caching functionality to HTTPX
 
+### httpx-secure
+
+[GitHub](https://github.com/Zaczero/httpx-secure)
+
+Drop-in SSRF protection for httpx with DNS caching and custom validation support.
+
 ### httpx-socks
 
 [GitHub](https://github.com/romis2012/httpx-socks)