feat(frontend): add footer with version number

frontend/src/components/Footer.tsx

@@ -0,0 +1,33 @@
+import React from "react";
+
+const REPO_URL = "https://github.com/apricote/Listory";
+const CHANGELOG_URL = `${REPO_URL}/blob/master/CHANGELOG.md`;
+
+const VERSION = process.env.REACT_APP_VERSION || "Unknown";
+
+export const Footer: React.FC = () => {
+  return (
+    <div className="flex items-center justify-between flex-wrap bg-green-500 p-4 text-green-200 hover:text-white text-xs">
+      <div>
+        <a
+          href={CHANGELOG_URL}
+          target="_blank"
+          rel="noreferrer"
+          title="Listory Changelog"
+        >
+          v{VERSION}
+        </a>{" "}
+      </div>
+      <div>
+        <a
+          href={REPO_URL}
+          target="_blank"
+          rel="noreferrer"
+          title="Listory GitHub Repository"
+        >
+          Check out on GitHub
+        </a>
+      </div>
+    </div>
+  );
+};