docs: add documentation for http and lsjson

docs/content/commands/rclone_lsjson.md

@@ -56,7 +56,8 @@ Different options may also affect which properties are included:
   properties will be omitted - even for encrypted remotes.
 - If `--metadata` is set then an additional Metadata property will be
   returned. This will have [metadata](/docs/#metadata) in rclone standard format
-  as a JSON object.
+  as a JSON object. Also, if `--metadata` is set then name of the file can be
+  taken from the metadata field "content-disposition" if the remote supports it.
 
 The default is to list directories and files/objects, but this can be changed
 with the following options:

docs/content/http.md

@@ -235,6 +235,16 @@ Properties:
 - Type:        string
 - Required:    false
 
+### Metadata
+
+Here are the possible system metadata items for the http backend.
+
+| Name | Help | Type | Example | Read Only |
+|------|------|------|---------|-----------|
+| content-disposition | Content-Disposition header | string | inline | N |
+
+See the [metadata](/docs/#metadata) docs for more info.
+
 ## Backend commands
 
 Here are the commands specific to the http backend.