feat: add author metadata to zebbern security skills (#8)

Added metadata block with author: zebbern and version: 1.1 to all 29 security skills originally from claude-code-guide repository:
- active-directory-attacks, api-fuzzing-bug-bounty, aws-penetration-testing
- broken-authentication, burp-suite-testing, cloud-penetration-testing
- ethical-hacking-methodology, file-path-traversal, html-injection-testing
- idor-testing, linux-privilege-escalation, linux-shell-scripting
- metasploit-framework, network-101, pentest-checklist, pentest-commands
- privilege-escalation-methods, red-team-tools, scanning-tools
- shodan-reconnaissance, smtp-penetration-testing, sql-injection-testing
- sqlmap-database-pentesting, ssh-penetration-testing, top-web-vulnerabilities
- windows-privilege-escalation, wireshark-analysis, wordpress-penetration-testing
- xss-html-injection

skills/smtp-penetration-testing/SKILL.md

@@ -1,6 +1,9 @@
 ---
 name: SMTP Penetration Testing
 description: This skill should be used when the user asks to "perform SMTP penetration testing", "enumerate email users", "test for open mail relays", "grab SMTP banners", "brute force email credentials", or "assess mail server security". It provides comprehensive techniques for testing SMTP server security.
+metadata:
+  author: zebbern
+  version: "1.1"
 ---
 
 # SMTP Penetration Testing