premiumizeme: use lib/encoder

docs/content/premiumizeme.md

@@ -88,6 +88,19 @@ premiumize.me does not support modification times or hashes, therefore
 syncing will default to `--size-only` checking.  Note that using
 `--update` will work.
 
+#### Restricted filename characters
+
+In addition to the [default restricted characters set](/overview/#restricted-characters)
+the following characters are also replaced:
+
+| Character | Value | Replacement |
+| --------- |:-----:|:-----------:|
+| \         | 0x5C  | ＼           |
+| "         | 0x22  | ＂           |
+
+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/premiumizeme/premiumizeme.go then run make backenddocs -->
 ### Standard Options