qingstor: use lib/encoder

docs/content/qingstor.md

@@ -126,6 +126,15 @@ credentials. In order of precedence:
      - Access Key ID: `QS_ACCESS_KEY_ID` or `QS_ACCESS_KEY`
      - Secret Access Key: `QS_SECRET_ACCESS_KEY` or `QS_SECRET_KEY`
 
+### Restricted filename characters
+
+The control characters 0x00-0x1F and / are replaced as in the [default
+restricted characters set](/overview/#restricted-characters).  Note
+that 0x7F is not replaced.
+
+Invalid UTF-8 bytes will also be [replaced](/overview/#invalid-utf8),
+as they can't be used in JSON strings.
+
 <!--- autogenerated options start - DO NOT EDIT, instead edit fs.RegInfo in backend/qingstor/qingstor.go then run make backenddocs -->
 ### Standard Options