Resize videos in HTML like we do images now.

This is probably *fairly* useless, since no browsers as far as I know
support the video tag, but not CSS. But it could make a basic CSS
theme a few lines shorter.

brutaldon/templates/main/toot_partial.html

@@ -121,6 +121,7 @@
                     {% else %}
                     <figure class="column">
                       <video controls loop class="is-max-256"
+                             width="256" height="256"
                                poster="{{ media.preview_url }}">
                             <source src="{{ media.url }}" type="video/mp4">
                             <a href="{{ media.url }}">