Add FreeBSD port from the development-repo

Summary: * FreeBSD now has a port for this in kde@FreeBSD.org's development repo.

Reviewers: #freebsd, mvourlakos

Reviewed By: mvourlakos

Subscribers: plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D8302

README.md

@@ -81,6 +81,8 @@ We recommend that you use at least **Plasma 5.9.0**
 
 - [Void Linux package](https://github.com/voidlinux/void-packages/tree/master/srcpkgs/latte-dock)
 
+### FreeBSD
+- [FreeBSD Port - official](https://www.freshports.org/deskutils/latte-dock/)
 
 See the [installation instruction](INSTALLATION.md) for others Linux distribution or development build