Adds alt tags to img tags that were missing them.

[charliepark]

This just adds an empty "alt" attribute on tags, so screen readers won't read out the janky file path / file name. In each of these cases, there's a link nearby to the profile's page, using the profile name as the text of the link. So it's okay (preferred, even) for screen readers to silently drop these links.

[waxpancake]

Great! Thanks, @charliepark!