Feat: adds PaymentItemType enum and PaymentItem.type

 * closes #163

Author: marcoscaceres

index.html

@@ -281,6 +281,7 @@ 
               {
                 label: "Sales Tax",
                 amount: { currency: "USD", value: "5.00" },
+                type: "tax"
               },
             ],
             total: {
@@ -1853,6 +1854,7 @@ 
           required DOMString label;
           required PaymentCurrencyAmount amount;
           boolean pending = false;
+          PaymentItemType type;
         };
       pre>
       <p>
@@ -1885,6 +1887,39 @@ 
           shipping option. <a>User agentsa> MAY indicate pending fields in
           the user interface for the payment request.
         dd>
+        <dt>
+          <dfn>typedfn> member
+        dt>
+        <dd>
+          A <a>PaymentItemTypea> enum value. A the value of <a>typea> to
+          assist in the presentation of <a>PaymentItema> by, for example,
+          visually grouping types together or other otherwise distinguishing
+          them from other types (or from items that have no associated type).
+        dd>
+      dl>
+    section>
+    <section data-dfn-for="PaymentItemType">
+      <h2>
+        <dfn>PaymentItemTypedfn> enum
+      h2>
+      <pre class="idl">
+        enum PaymentItemType {
+          "tax"
+        };
+      pre>
+      <p>
+        The <a>PaymentItemTypea> serves to categorize a <a>PaymentItema>
+        into particular types.
+      p>
+      <dl>
+        <dt>
+          "<dfn>taxdfn>"
+        dt>
+        <dd>
+          Indicates that the corresponding <a>PaymentItema> represents a form
+          of tax (e.g., sales tax, goods and services tax, value added tax,
+          etc.).
+        dd>
       dl>
     section>
     <section data-dfn-for="PaymentAddress" data-link-for="PaymentAddress">