Editorial: Add Oxford comma and fix variable markup (#1001)

Author: anba

spec/datetimeformat.html

@@ -1257,7 +1257,7 @@ <h1>
                 1. If _formatProp_ is *"shortOffset"*, set _score_ to _score_ - _offsetPenalty_.
                 1. Else if _formatProp_ is *"longOffset"*, set _score_ to _score_ - (_offsetPenalty_ + _shortMorePenalty_).
                 1. Else if _optionsProp_ is *"short"* and _formatProp_ is *"long"*, set _score_ to _score_ - _shortMorePenalty_.
-                1. Else if _optionsProp_ is *"shortGeneric"* and _formatProp_ is *"longGeneric"*, set _score_ to _score - _shortMorePenalty_.
+                1. Else if _optionsProp_ is *"shortGeneric"* and _formatProp_ is *"longGeneric"*, set _score_ to _score_ - _shortMorePenalty_.
                 1. Else if _optionsProp_ ≠ _formatProp_, set _score_ to _score_ - _removalPenalty_.
               1. Else if _optionsProp_ is *"shortOffset"* and _formatProp_ is *"longOffset"*, then
                 1. Set _score_ to _score_ - _shortMorePenalty_.

spec/pluralrules.html

@@ -261,7 +261,7 @@ <h1>
       </h1>
       <dl class="header">
         <dt>description</dt>
-        <dd>The returned String characterizes the plural category of _s_ according to _locale_, _type_ and _notation_.</dd>
+        <dd>The returned String characterizes the plural category of _s_ according to _locale_, _type_, and _notation_.</dd>
       </dl>
     </emu-clause>