procstat: add page (#15738)

Co-authored-by: Lena <126529524+acuteenvy@users.noreply.github.com>

pages/freebsd/procstat.md

@@ -0,0 +1,20 @@
+# procstat
+
+> Display detailed information about processes in FreeBSD.
+> More information: <https://man.freebsd.org/cgi/man.cgi?query=procstat>.
+
+- Display file descriptors of a specific process:
+
+`procstat fds {{pid}}`
+
+- Show virtual memory mappings of a process:
+
+`procstat vm {{pid}}`
+
+- Display process arguments:
+
+`procstat arguments {{pid}}`
+
+- Show resource limits of a process:
+
+`procstat rlimit {{pid}}`