[Feature] Enum for tags

We declare tags for game events and we want to group them and use word completion like it works with vars and functions.

We can declare TAGS for example:
```
TAGS Background = school_class, school_hall, home
```

And use it like this:
```
# Background.school_class
```

It is very good feature for group game events and meta data. Also no need to remember all your tag names for taping them cause we use word completion.