Handbook - Ports: Add example port FLAVOR notation

Add example of port FLAVOR notation in poudriere port-list

Reviewed by:            fernape@
Pull Request:           #197

documentation/content/en/books/handbook/ports/_index.adoc

@@ -1195,12 +1195,13 @@ The basic configuration shown here puts a single jail-, port-, and set-specific
 The filename in this example is created by combining the jail name, port name, and set name: `13amd64-local-workstation-make.conf`.
 The system `make.conf` and this new file are combined at build time to create the `make.conf` used by the build jail.
 
-Packages to be built are entered in `13amd64-local-workstation-pkglist`:
+Packages to be built are entered in `13amd64-local-workstation-pkglist` (ports with extref:{porters-handbook}flavors[FLAVORS] can be defined with @FLAVOR):
 
 [.programlisting]
 ....
 editors/emacs
 devel/git
+devel/php-composer2@php82
 ports-mgmt/pkg
 ...
 ....