docs: document "extended" argument for GET directory endpoint

Signed-off-by:  Eric Callahan <arksine.code@gmail.com>

docs/api_changes.md

@@ -1,6 +1,12 @@
 This document keeps a record of all changes to Moonraker's remote
 facing APIs.
 
+### November 2nd 2020
+- The `GET /server/files/directory` endpoint now accepts a new
+  optional argument, `extended`.  If `extended=true`, then
+  the data returned for gcode files will also include extracted
+  metadata if it exists.
+
 ### October 25th 2020
 - The `modified` field reported for files and directories is no
   longer represented as a string.  It is now a floating point

docs/web_api.md

@@ -483,18 +483,23 @@ Unlike `/server/files/list`, this command does not walk through
 subdirectories.
 
 - HTTP command:\
-  `GET /server/files/directory?path=gcodes/my_subdir`
+  `GET /server/files/directory?path=gcodes/my_subdir&extended=true`
 
   If the query string is omitted then the command will return
   the "gcodes" file list by default.
 
 - Websocket command:\
   `{jsonrpc: "2.0", method: "server.files.get_directory",
-   params: {path: "gcodes/my_subdir"} , id: <request id>}`
+   params: {path: "gcodes/my_subdir", extended: true} ,
+   id: <request id>}`
 
   If the "params" are omitted then the command will return
   the "gcodes" file list by default.
 
+The `extended` argument is optional, and defaults to false. If
+specified and set to true, then data returned for gcode files
+will also include metadata if it is available.
+
 - Returns:\
   An object containing file and subdirectory information in the
   following format: