Add CIDR support for expr (#62)

* feat: add cidr support for expr

* docs: add example for cidr

* minor code tweaks

---------

Co-authored-by: Toby <tobyxdd@gmail.com>

README.ja.md

@@ -130,6 +130,10 @@ workers:
 - name: block CN geoip
   action: block
   expr: geoip(string(ip.dst), "cn")
+
+- name: block cidr
+  action: block
+  expr: cidr(string(ip.dst), "192.168.0.0/16")
 ```
 
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