Currently we're using a list of MIME types for `accept` attribute on `input[type="file"]` for filter options of file picker, and actual file extensions will be infered by browsers. However, infered extensions may not include our expected items. For example, "image/jpeg" seems to be infered to
only ".jfif" extension in Firefox.

To ensure common file extensions are in the list, this PR adds file extensions in addition to MIME types. Also having items in both format is encouraged by HTML5 spec.

https://www.w3.org/TR/html5/forms.html#file-upload-state-(type=file)