The post-tag is added automatically if that is found a content when saving post. Moreover, some similar words can be set to a post-tag.
"Add New Tag" and "Edit Tag" form is extended, the similar word field is added.
"Tags" list is extended, the similar words field is added.
New post is written in and published.
"Drink" and "Food" were added to the Tags widget.
"all tags contained in it are added" is clicked when adding a post-tag to the past posts.