[Docker] Docker tag

Docker tag

With the following command, we create a new image from the old docker tag, and assign it to a new docker tag.
```
  docker tag ad-website:latest ad-website:1
```
After we do this, we get two images referencing the same docker tag, which help us not lose the previous image's version when we create a new image tagged with the same tag(usually latest).
```
  docker build -t ad-website:latest .
```

#docker