feat: add log file to thinkfan-service in (radix services linux)

modules/radix/services/linux.scm

@@ -39,7 +39,8 @@
                                    #~((string-append "-c" #$config-file))
                                    #~())
                             #$@extra-options)
-                     #:pid-file #$pid-file))
+                     #:pid-file #$pid-file
+                     #:log-file "/var/log/thinkfan.log"))
            (stop #~(make-kill-destructor))
            (one-shot? #t)
            (respawn? respawn?)))))