Filter directory by available output file formats

[adelevett]

Feature Description

Add Output Format (ePub, PDF, XML, Common Cartridge, etc.) as a selectable filter when searching the Pressbooks Directory.

Feature Use Case

Instructors are currently not able to filter search results by available output formats so if they have a specific limitation or need based on the class delivery format they have to manually inspect search results to check if their specific file format is available for the given OER.

Other Notes

As far as I know, there is not currently a way for OER content anywhere to be filtered by accessibility characteristics. For example, some instructors may not be able to use a given OER if the respective PDF is not tagged. If there was a way to filter both for file format and perhaps a set of machine readable accessibility flags (e.g. headings present and logically ordered, alt text for epub and PDF, tags for PDF) instructors would be able to make more informed choice when evaluating OER.

[SteelWagstaff]

Great idea @adelevett -- we should be able to add a visual indicator of some kind to the book cards in the Directory informing visitors whether exports files have been made available for download and if so, which file types are included. We could also add filters for this information. Will add this to our product backlog.