Set html `accept` attribute for file input form when `FileAllowed` is set for file upload

[PeterDaveHello]

Currently, the generated html for file doesn't seem to use html "accept" attribute, which will be helpful to guide the users to select the proper files(at least with the correct file extension).

As there is FileAllowed to set the allowed file extensions, maybe it'll be also great to set it on the form?

[azmeuk]

You can pass accept in the render_kw parameter:

    photo = FileField("Photo", render_kw={"accept": "image/*"})

[PeterDaveHello]

Thanks @azmeuk , I'll try it before it's supported to be set with FileAllowed!

[PeterDaveHello]

@azmeuk Is that clear that to support some config to set at one place and apply to both front-end and back-end will not be considered? Thanks!