Code.gs

function doPost(request){
  
  // get the sting value of the POST data
  var postJSON = request.postData.getDataAsString();
  var payload = JSON.parse(postJSON);
  var tag = payload.push_data.tag;
  var reponame = payload.repository.repo_name;
  var dockerimagename = payload.repository.name;

  
  if(typeof request !== 'undefined')

  MailApp.sendEmail({
     to: "yourmailid@gmail.com",
     subject: "New Docker Image Uploaded to the repository "+reponame,
    htmlBody: "Hi Team,<br>"+
              "Please find the Details of the Docker Image uploaded to the repository "+reponame+"<br>"+
              "<strong>Docker Name: " + dockerimagename+"<br>"+           
              "Docker Image version:" +tag+"<br></strong>"
               
    });
  
}