Assign null to alt for images

[nancymou]

User issue: The current alt text for images within "featured" and other exhibit cards in the Online Exhibits home page and images in search results have alternative text that shows a title + file name. The file name is not a useful alternative text for users.

Success Criteria Assign null alt text (alt="") or remove the file name extension for decorative images in:

• [x] Featured exhibit card and other exhibit cards in the Online Exhibits home page
• [x] Search Results page results.

[nancymou]

@bnhowell can you check the search page and let me know if the changes in the image are what you are looking for? https://nancymou.www.lib.umich.edu/online-exhibits-2.3/search?query=Arts

[nancymou]

@bnhowell This issue is fixed and available for test at https://beta3.www.lib.umich.edu/online-exhibits-2.5.1/

[bnhowell]

@nancymou This looks good!