request: Provide post-processing of filename via custom function

[andreaswittmann]

Reference: A similar problem was discussed and handled in #83 and #142 Problem: If a file that contains a filename with special characters like parentheses and German Umlauts is dragged to an org file, the uri in org-download-dnd is modified to contain characters beginning with %. While Emacs org-mode and Linux can handle the resulting links, problems occur with org-publish to HTML. The resulting link cannot be opened from the website, because the links are invalid. As a workaround I use the org-download-rename-last-file function. Since this manual approach is error prone I am asking for an extension. Proposal: Provide a customization that allows to post-process the filename with a custom function.