Add easywall to the Security section

[jp1337]

Adds easywall, a web interface for the Linux nftables firewall (Go, GPL-3.0).

• Features: open ports, blacklist/whitelist, port forwarding, custom nftables rules, audit log, Docker coexistence, multilanguage interface.
• Key differentiator: every apply reverts itself after 120 seconds unless it is confirmed — you cannot lock yourself out of the machine you are editing.
• Install: Debian/Ubuntu .deb (amd64 + arm64) and Docker; live demo and docs at easywall-project.org.

Entry line matches the section's format (source, license, language).