Add ENNA - security tool index with cheat sheets and starter kits

Project: ENNA (GitHub)

Index of 325+ security tools with getting started guides, cheat sheets (Nmap, Hashcat, SQLMap, John, etc.), and starter kits. Useful for finding and learning the right tools for CTF challenges.

Suggested entry (Tools section):

- [ENNA](https://www.en-na.com) - Index of 325+ security tools with cheat sheets, getting started guides, and starter kits for CTF players.

MIT licensed.