BugzillaA11yFixes: Set alt for user images.

The text is just "User image", but it eliminates overly verbose, ugly reporting due to screen reader guessing for unlabelled images.

Author: jcsteh

BugzillaA11yFixes.user.js

@@ -28,6 +28,10 @@ function tweak() {
 	// Comment numbers.
 	for (elem of document.getElementsByClassName("bz_comment_number"))
 		makeHeading(elem, 2);
+
+	// Label user images.
+	for (elem of document.querySelectorAll("span.bz_comment_user a img"))
+		elem.setAttribute("alt", "User image");
 }
 
 tweak();