cover: List curation:

- Reduce Padding around covers.
- Remove `content` which is applying too extensive default styles.
- Style headings.
- Replace table with definition list.
- Clip cover container to avoid caption overflowing.

bookwyrm/templates/snippets/book_cover.html

@@ -6,6 +6,7 @@
 <figure
     class="
         cover-container
+        is-clipped
         is-flex
         is-align-items-center