Now supports running under a sub path

Just set the SPOOLMAN_BASE_PATH environment variable and it should work.

Resolves #95

client/src/components/favicon.tsx

@@ -0,0 +1,20 @@
+import { useEffect } from "react";
+
+/**
+ * Renders a favicon element in the head of the HTML document with the specified URL.
+ *
+ * @param {string} props.url - The URL of the favicon image.
+ * @return {JSX.Element} - An empty JSX element.
+ */
+export function Favicon(props: { url: string }) {
+  useEffect(() => {
+    let link = document.querySelector("link[rel~='icon']") as HTMLLinkElement;
+    if (!link) {
+      link = document.createElement("link") as HTMLLinkElement;
+      link.rel = "icon";
+      document.getElementsByTagName("head")[0].appendChild(link);
+    }
+    link.href = props.url;
+  }, [props.url]);
+  return <></>;
+}