update docs

doc/en/scripting/builtins/libfile.md

@@ -139,6 +139,12 @@ file.create_zip(directory: str, output_file: str) --> str
 
 Creates a ZIP archive from the contents of the specified directory.
 
+```lua
+file.create_memory_device() --> str
+```
+
+Creates a memory file system and returns entry point name. Lives until content unload.
+
 ```lua
 file.name(path: str) --> str
 ```