This DrRacket plugin adds a Script menu to the main window.
This menu has several items, followed by the list of active scripts.

The New Script item asks for a script name and creates 2 files:
    - a .rkt file, the script itself (with a sample program)
    - a .rktd file, the metadata of the script with the default values
These two files are automatically opened.

The .rkt file:
    This is the script file.
    It must provide the 'transform-input-string' (that's not a very good name) 
    function, as in the sample code.
    It is meant to be executable by itself, to ease the testing process.

The .rktd file:
    - most options are the same as for the menu-item% constructor
    - sub-menu: a string for the label of the sub-menu in which the script 
    will appear
    - new-tab: if #t the result of the script is output in a new tab and not 
    in the current window

The script menu is rebuild each time the user activates it, so that changes
are taken into account as soon as possible.

The directory of the user scripts can be change through DrRacket's preferences
(Edit/Preferences/Scripts).