Footer: add alt text for icons

src/components/Footer.astro

@@ -1,12 +1,30 @@
 <footer>
   <a href="https://m.comfycamp.space/@lumin" rel="me" target="_blank">
-    <img src="/icons/mastodon.svg" width="18px" height="18px" /> Mastodon
+    <img
+      src="/icons/mastodon.svg"
+      width="18px"
+      height="18px"
+      alt="Mastodon logo"
+    />
+    Mastodon
   </a>
   <a href="https://matrix.to/#/@lumin:matrix.comfycamp.space" target="_blank">
-    <img src="/icons/matrix.svg" width="18px" height="18px" /> Matrix
+    <img
+      src="/icons/matrix.svg"
+      width="18px"
+      height="18px"
+      alt="Matrix logo"
+    />
+    Matrix
   </a>
   <a href="https://github.com/ordinary-dev/comfycamp/issues/new" target="_blank">
-    <img src="/icons/github.svg" width="18px" height="18px" /> Обратная связь
+    <img
+      src="/icons/github.svg"
+      width="18px"
+      height="18px"
+      alt="Github logo"
+    />
+    Обратная связь
   </a>
 </footer>