Add Readme to plugin's bundled documentation

[mcascone]

From the docs:

It is also possible (and strongly recommended) to add a user manual to the dsp script. It will be made available to the end user in the title bar, with an additional question mark icon (see the chapter about user interface for more details).

Both pdf and html manuals are supported for scripts loaded into Plug'n Script (whereas only pdf is supported for exported plug- ins).

Simply distribute the script with an html or pdf file in the same directory as the script, with the appropriate naming convention:the manual should have the same name as the script file, with the .html or .pdf extension. For example: myscript.cxx and myscript.pdf.

If no manual is provided, the help icon will not be visible in Plug'n Script or in the exported plug- in. Note: exported plug- ins currently support pdf manuals only.