Minor typo.

Author: davidlehn

spec/latest/json-ld/index.html

@@ -3436,7 +3436,7 @@ <h2>Id Maps</h2>
   <section class="changed">
     <h2>Type Maps</h2>
 
-    <p>An <a>type map</a> is used to associate an <a>IRI</a> with a value that allows easy
+    <p>A <a>type map</a> is used to associate an <a>IRI</a> with a value that allows easy
       programatic access. A <a>type map</a> may be used as a term value within a <a>node object</a> if the <a>term</a>
       is defined with <code>@container</code> set to <code>@type</code>. The keys of a <a>type map</a> MUST be <a>IRIs</a>
       (<a>relative IRI</a>, <a>compact IRI</a> (including <a>blank node identifiers</a>), or <a>absolute IRI</a>)