add kqueue to docs

examples/all/all_posix.odin

@@ -1,6 +1,8 @@
 #+build darwin, openbsd, freebsd, netbsd
 package all
 
-import posix "core:sys/posix"
+import posix  "core:sys/posix"
+import kqueue "core:sys/kqueue"
 
 _ :: posix
+_ :: kqueue