async function uploadScreenshot(issueUri, screenshotUri) {
  const dlResonse = await fetch(screenshotUri);
  if (!dlResonse.ok) {
    throw new Error("Screenshot download failed: " +
                    `${dlResonse.status} ${dlResonse.statusText}`);
  }
  const blob = await dlResonse.blob();

  const form = new FormData();
  form.append("file", blob, "screenshot.png");
  const ulResponse = await fetch(issueUri + "/attachments", {
    method: "POST",
    body: form,
    headers: {
      "Authorization": authHeader(),
      "Accept": "application/json",
      "X-Atlassian-Token": "no-check",
    },
  });
  if (!ulResponse.ok) {
    throw new Error("Screenshot upload failed: " +
                    `${ulResponse.status} ${ulResponse.statusText}`);
  }
}
Uploads screenshot to Jira (after downloading it from Firebase).
@param {string} issueUri URI of the Jira issue
@param {string} screenshotUri URI of the screenshot hosted by Firebase