improve api ref docs seo

Author: sbiscigl

docs/doxygen/static/docs_header.html

@@ -6,6 +6,9 @@
 <meta http-equiv="X-UA-Compatible" content="IE=11"/>
 <meta name="generator" content="Doxygen $doxygenversion"/>
 <meta name="viewport" content="width=device-width, initial-scale=1"/>
+<meta name="guide-name" content="AWS SDK for C++ v1 API Reference"/>
+<meta name="service-name" content="AWS SDK for C++ v1"/>
+<meta name="description" content="$title - AWS SDK for C++ v1">
 <!--BEGIN PROJECT_NAME--><title>$projectname: $title</title><!--END PROJECT_NAME-->
 <!--BEGIN !PROJECT_NAME--><title>$title</title><!--END !PROJECT_NAME-->
 <link href="$relpath^tabs.css" rel="stylesheet" type="text/css"/>