tweak z-index of images

lib/figures.typ

@@ -23,6 +23,7 @@
       right: 0;
       left: 0;
       position: fixed;
+      z-index: 2;
 
       background: var(--color-bg-overlay);
 
@@ -31,6 +32,7 @@
       flex-direction: column;
 
       img {
+        position: fixed;
         width: 95dvw;
         height: 95dvh;
         max-width: 95dvw;
@@ -54,6 +56,7 @@
 
     image-alt-group {
       position: relative;
+      z-index: 1;
       display: inline-block;
 
       .alt-text {
@@ -65,7 +68,7 @@
         top: 0;
         border-radius: 6px;
         position: absolute;
-        z-index: 1;
+        z-index: 3;
 
         transition: opacity 250ms ease-in, visibility 0ms ease-in 250ms;