CI: Install pkg-config for FreeBSD build

This allows configure to be generated with pkg.m4 in FreeBSD build job.

Author: Explorer09

.github/workflows/ci.yml

@@ -233,7 +233,7 @@ jobs:
             release: '14.1'
             usesh: true
             prepare: |
-              pkg install -y gmake autoconf automake git
+              pkg install -y gmake autoconf automake pkgconf git
               git config --global --add safe.directory /home/runner/work/htop/htop
             run: |
               set -e