function doGet(e) {
  try {
    const targetUrl = getTargetUrl_(e);
    if (!isAllowedUrl_(targetUrl)) {
      throw new Error("Only siatube.com is allowed");
    }a
    const response = UrlFetchApp.fetch(targetUrl, {
      method: "get",
      muteHttpExceptions: true,
      followRedirects: true,
    });
    const contentType =
      response.getHeaders()["Content-Type"] ||
      response.getHeaders()["content-type"] ||
      "text/plain";
    return ContentService
      .createTextOutput(response.getContentText())
      .setMimeType(getMimeType_(contentType));
  } catch (error) {
    return ContentService
      .createTextOutput(JSON.stringify({
        ok: false,
        error: error.message,
      }))
      .setMimeType(ContentService.MimeType.JSON);
  }
}

function getTargetUrl_(e) {
  const queryString =
    e && e.queryString
      ? String(e.queryString)
      : "";
  if (queryString.indexOf("url=") !== 0) {
    throw new Error("url is required");
  }
  let targetUrl = queryString.substring(4);
  if (!targetUrl) {
    throw new Error("url is required");
  }
  if (
    targetUrl.indexOf("https://") !== 0 &&
    targetUrl.indexOf("http://") !== 0
  ) {
    try {
      const decoded = decodeURIComponent(targetUrl);
      if (
        decoded.indexOf("https://") === 0 ||
        decoded.indexOf("http://") === 0
      ) {
        targetUrl = decoded;
      }
    } catch (_) {}
  }
  return targetUrl;
}

function isAllowedUrl_(targetUrl) {
  return (
    targetUrl.indexOf("https://siatube.com/") === 0 ||
    targetUrl === "https://siatube.com"
  );
}

function getMimeType_(contentType) {
  const type = String(contentType).toLowerCase();
  if (type.indexOf("application/json") !== -1) {
    return ContentService.MimeType.JSON;
  }
  if (
    type.indexOf("application/javascript") !== -1 ||
    type.indexOf("text/javascript") !== -1
  ) {
    return ContentService.MimeType.JAVASCRIPT;
  }
  if (type.indexOf("text/csv") !== -1) {
    return ContentService.MimeType.CSV;
  }
  if (
    type.indexOf("application/xml") !== -1 ||
    type.indexOf("text/xml") !== -1
  ) {
    return ContentService.MimeType.XML;
  }
  return ContentService.MimeType.TEXT;
}

<script defer data-domain="html.cafe" src="https://milkymouse.com/js/script.js"></script>