mailru: use lib/encoder

docs/content/mailru.md

@@ -134,6 +134,25 @@ This command does not take any path arguments.
 To view your current quota you can use the `rclone about remote:`
 command which will display your usage limit (quota) and the current usage.
 
+#### Restricted filename characters
+
+In addition to the [default restricted characters set](/overview/#restricted-characters)
+the following characters are also replaced:
+
+| Character | Value | Replacement |
+| --------- |:-----:|:-----------:|
+| "         | 0x22  | ＂          |
+| *         | 0x2A  | ＊          |
+| :         | 0x3A  | ：          |
+| <         | 0x3C  | ＜          |
+| >         | 0x3E  | ＞          |
+| ?         | 0x3F  | ？          |
+| \         | 0x5C  | ＼          |
+| \|        | 0x7C  | ｜          |
+
+Invalid UTF-8 bytes will also be [replaced](/overview/#invalid-utf8),
+as they can't be used in JSON strings.
+
 ### Limitations ###
 
 File size limits depend on your account. A single file size is limited by 2G