We now prevent these variations:
* <hr/>
* <hr />
* <br/>
* <br />
We could enforce similar consistency for other void
tags, if we wished, but these two are particularly
prevalent.
The alt text of the leading images were displayed as preview
content in inbox by email clients like gmail. Since the leading
images were used mostly for decoration this made the preview
content gibberish. It's fine to set the alt attributes to empty
from accessibility point of view since the old alt attributes
did't added any meaningful information.