!.md

UrlFetchApp wrapper https://github.com/oshliaer/fetch

createPost.gs

function createPost() {
  var content = DocumentApp.openById("1BVEqtuXPmDf3ruLKfeYlkSoDCrDkGLdJpLkHxGwoyqg").getBody().getText();
  var options = {
    payload: {
      "kind": "blogger#post",
      "blog": {
        "id": "7091170028680816449"
      },
      "title": "A new post",
      "content": content
    },
  }
  var response = Fetch.post("https://www.googleapis.com/blogger/v3/blogs/7091170028680816449/posts", options);
  Logger.log(response.getContentText())
}

getBlog.gs

function getBlog() {
  var response = Fetch.get("https://www.googleapis.com/blogger/v3/blogs/7091170028680816449");
  Logger.log(response.getContentText())
}

updatePost.gs

function updatePost() {
  //  var docExport = Drive.Files.get("1BVEqtuXPmDf3ruLKfeYlkSoDCrDkGLdJpLkHxGwoyqg").exportLinks["text/html"];
  //  var content = Fetch.get(docExport).getContentText();
  var doc = DocumentApp.openById("1BVEqtuXPmDf3ruLKfeYlkSoDCrDkGLdJpLkHxGwoyqg");
  var content = doc.getBody().getText();
  var title = doc.getName();
  var options = {
    payload: {
      "kind": "blogger#post",
      "id": "5780301629671909223",
      "blog": {
        "id": "7091170028680816449"
      },
      "title": title,
      "content": content
    },
  }
  var response = Fetch.put("https://www.googleapis.com/blogger/v3/blogs/7091170028680816449/posts/5780301629671909223", options);
  Logger.log(response.getContentText())
}