add missing "alt" in <img> tags

Author: artemp

pages/media.html

@@ -12,11 +12,11 @@ <h2>Mapnik typeface and logo mark</h2>
 
 Mapnik's new modern typeface and logo mark is powerful, modern, and flexible. Much like Mapnik itself. We primarily use the Maven Pro font family with Open Sans Light for it's simple elegance.
 
-<img src="{{site.baseurl}}/images/assets/mapnik_typefaces.png">
+<img alt="Mapnik typefaces" src="{{site.baseurl}}/images/assets/mapnik_typefaces.png">
 
 
 <h2>Mapnik colors</h2>
 
-<img src="{{site.baseurl}}/images/assets/mapnik_colors.png">
+<img alt="Mapnik colors" src="{{site.baseurl}}/images/assets/mapnik_colors.png">
 
 <p>Download <a href="{{site.baseurl}}/images/assets/mapnik_brand-assets.zip">Mapnik brand assets</a></p>