Base64 to Blob (es6)
const b64toBlob = async (b64Data, contentType = 'application/octet-stream') => {
const url = `data:${contentType};base64,${b64Data}`;
const response = await fetch(url);
const blob = await response.blob();
return blob;
};
// https://stackoverflow.com/a/36183085/1167442