fix(gallery): adjust image sizing to fit window height

Update gallery image styles to use max-height based on window minus nav,
max-width 100%, and auto width for proper scaling with contain fit.

Signed-off-by: Sped0n <hi@sped0n.com>

assets/scss/_partial/_gallery.scss

@@ -25,8 +25,9 @@
   }
 
   img {
-    width: 100%;
-    height: 100%;
+    max-height: calc(var(--window-height) - 2 * var(--nav-height));
+    max-width: 100%;
+    width: auto;
     object-fit: contain;
   }