add noise options for freedom (#565)

docs/en/config/outbounds/freedom.md

@@ -14,6 +14,10 @@ Freedom is an outbound protocol that can be used to send (normal) TCP or UDP dat
     "length": "100-200",
     "interval": "10-20" // ms
   },
+  "noise": {
+    "packet": "rand:5-10",
+    "delay": "10-20" // ms
+  },
   "proxyProtocol": 0
 }
 ```
@@ -57,6 +61,14 @@ A key-value map used to control TCP fragmentation，under some circumstances it
 
 `"interval"`: time between fragments（ms）
 
+> `noise`: map
+
+A key-value map used to control UDP noise，under some circumstances it can bypass some udp based protocol restrictions.
+
+`"packet"`：support two different methods."rand:min-max" generates random bytes with min and max length provided for noise."str:Customstring" will use user input string as noise.
+
+`"delay"`：delay before sending real data (ms).If not specified, the default value is 0.
+
 > `proxyProtocol`: number
 
 The value of `proxyProtocol` represents the PROXY Protocol version. default value is `0`.