Ability to define file name in code listing snippet

[szpak]

Sometimes, I would like to place 2 or 3 code snippets and it is important for people which file is which and what are the file names.

I would be good to be able to redefine a default code snippet header with a file name. For example, instead of:

I would like to be able to have "SpockConfig.groovy" used instead of "Groovy" in the header.

The parameter could be passed as the others, e.g.

    ```groovy {hl_lines=[6,9,17], file_name="SpockConfig.groovy"}
        //my source code
    ```