Add API documentation and underground station importer

- Introduced a new HTML documentation page for the oradio API, including a JavaScript file to handle dynamic content and API requests.
- Added a CSS file for styling the documentation page.
- Implemented an underground station importer script that fetches data from Radio-Browser and writes it to a JSON file.
- Created a stats module to compute and manage vote and play statistics for radio stations.
- Added a polyfill for modulepreload to ensure compatibility with older browsers.

web/shared/api.js

@@ -1,21 +1,21 @@
 async function http(method, path, body) {
-  const res = await fetch(path, {
-    method,
-    credentials: 'same-origin',
-    headers: body ? { 'Content-Type': 'application/json' } : {},
-    body: body ? JSON.stringify(body) : undefined
-  });
-  if (res.status === 204) return null;
-  const ct = res.headers.get('content-type') || '';
-  const data = ct.includes('json') ? await res.json() : await res.text();
-  if (!res.ok) throw Object.assign(new Error(data?.error || res.statusText), { status: res.status, data });
-  return data;
+    const res = await fetch(path, {
+        method,
+        credentials: 'same-origin',
+        headers: body ? { 'Content-Type': 'application/json' } : {},
+        body: body ? JSON.stringify(body) : undefined
+    });
+    if (res.status === 204) return null;
+    const ct = res.headers.get('content-type') || '';
+    const data = ct.includes('json') ? await res.json() : await res.text();
+    if (!res.ok) throw Object.assign(new Error(data?.error || res.statusText), { status: res.status, data });
+    return data;
 }
 
 export const api = {
-  get: (p) => http('GET', p),
-  post: (p, b) => http('POST', p, b),
-  put: (p, b) => http('PUT', p, b),
-  patch: (p, b) => http('PATCH', p, b),
-  del: (p) => http('DELETE', p)
+    get: (p) => http('GET', p),
+    post: (p, b) => http('POST', p, b),
+    put: (p, b) => http('PUT', p, b),
+    patch: (p, b) => http('PATCH', p, b),
+    del: (p) => http('DELETE', p)
 };