Support image alt text

Fixes #559

src/sass/tweet/media.scss

@@ -4,7 +4,6 @@
   display: flex;
   flex-direction: row;
   flex-wrap: nowrap;
-  align-items: center;
   overflow: hidden;
   flex-grow: 1;
   max-height: 379.5px;
@@ -13,7 +12,7 @@
 
   .still-image {
     width: 100%;
-    display: flex;
+    align-self: center;
   }
 }
 
@@ -58,7 +57,6 @@
 .still-image {
   max-height: 379.5px;
   max-width: 533px;
-  justify-content: center;
 
   img {
     object-fit: cover;
@@ -69,8 +67,37 @@
   }
 }
 
+.alt-text {
+  margin: 0px;
+  padding: 11px 7px;
+  box-sizing: border-box;
+  position: absolute;
+  bottom: 10px;
+  left: 10px;
+  width: 2.98em;
+  max-height: 25px;
+  white-space: pre;
+  overflow: hidden;
+  border-radius: 10px;
+  color: var(--fg_color);
+  font-size: 12px;
+  font-weight: bold;
+  background: rgba(0, 0, 0, 0.5);
+  backdrop-filter: blur(12px);
+}
+
+.alt-text:hover {
+  padding: 7px;
+  width: Min(230px, calc(100% - 10px * 2));
+  max-height: calc(100% - 10px);
+  line-height: 1.2em;
+  white-space: pre-wrap;
+  transition-duration: 0.4s;
+  transition-property: max-height;
+}
+
 .image {
-  display: inline-block;
+  display: flex;
 }
 
 // .single-image {