[css-scroll-snap-1] Default 2nd to 1st value in scroll padding/margin shorthands

Author: cdoublev

css-scroll-snap-1/Overview.bs

@@ -1162,6 +1162,8 @@ Flow-relative Longhands for 'scroll-padding'  {#padding-longhands-logical}
     If two values are specified, the first gives the start value
     and the second gives the end value.
 
+    If only one value is specified, the second value defaults to the same value.
+
 Physical Longhands for 'scroll-margin'  {#margin-longhands-physical}
 --------------------------------------------------------------------
 
@@ -1219,6 +1221,8 @@ Flow-relative Longhands for 'scroll-margin'  {#margin-longhands-logical}
     If two values are specified, the first gives the start value
     and the second gives the end value.
 
+    If only one value is specified, the second value defaults to the same value.
+
 Privacy and Security Considerations {#priv-sec}
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