How can I allow certain file types to be uploaded in the Extra Question Field plugin?
Also I want to show the user an error which says " Only X, Y, and Z file types are allowed." (in red color) when the user wants to upload a file type other than what I mean.
I mean by file types this file extensions: tex, bbl, doc, jpg, pdf, png, txt, zip, ftx, log, bst, bib, cls, sty.
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