Re: [csswg-drafts] [css-align] Add shorthands for alignment properties

So, this:
```
place-items: <'align-items'> <'justify-items'> ;
place-self: <'align-self'> <'justify-self'> ;
place-content: <'align-content'> <'justify-content'>;
```
where only single values are allowed. 

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