Fix a typo.

Author: jyasskin

main.html

@@ -54,7 +54,7 @@ <h1>Scope</h1>
     standardized, and others may be standardized in a substantially
     changed form.</p>
 
-    <p>The goal of this technical specification it to build more
+    <p>The goal of this technical specification is to build more
     widespread existing practice for an expanded C++ standard
     library. It gives advice on extensions to those vendors who wish
     to provide them.</p>