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

**Project:** [ENNA](https://www.en-na.com) ([GitHub](https://github.com/1oosedows/enna))

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.

Open the repository's Tools section and review nearby entries for formatting and placement. Add the suggested ENNA link and description, then verify the Markdown renders correctly and the entry appears in the intended section.

Written by the indexing model from the issue text.