[css-align] Fix justify-items to correctly add left/right manually; fix place-items to match place-content/self. Fixes #2275

Author: tabatkins

css-align-3/Overview.bs

@@ -1682,7 +1682,7 @@ Inline/Main-Axis Alignment: the 'justify-items' property</h3>
 
 	<pre class="propdef">
 	Name: justify-items
-	Value: normal | stretch | <<baseline-position>> | [ <<overflow-position>>? <<self-position>> ] | [ legacy || [ left | right | center ] ]
+	Value: normal | stretch | <<baseline-position>> | <<overflow-position>>? [ <<self-position>> | left | right ] | legacy | legacy && [ left | right | center ]
 	Initial: legacy
 	Applies to: all elements
 	Inherited: no
@@ -1741,7 +1741,7 @@ Self-Alignment Shorthand: the 'place-items' property</h3>
 
 	<pre class="propdef">
 	Name: place-items
-	Value: [ normal | stretch | <<baseline-position>> | <<self-position>> ] [ normal | stretch | <<baseline-position>> | <<self-position>> ]?
+	Value: <'align-items'> <'justify-items'>?
 	Initial: see individual properties
 	Applies to: all elements
 	Inherited: no