Merge pull request #447 from graalvm/gradinac/improve-docs-header

Display the GraalVM logo on the generated NBT docs

docs/src/docs/asciidoc/docinfo.html

@@ -0,0 +1,5 @@
+<meta property="og:image" content="https://www.graalvm.org/resources/img/graalvm.png" />
+<meta name="description" content="The Native Build Tools project provides plugins for different build tools to add support for building and testing native applications written in Java (or any other language compiled to JVM bytecode)."/>
+<link rel="apple-touch-icon" sizes="180x180" href="https://www.graalvm.org/resources/img/favicon/apple-touch-icon.png">
+<link rel="icon" type="image/png" sizes="32x32" href="https://www.graalvm.org/resources/img/favicon/favicon-32x32.png">
+<link rel="icon" type="image/png" sizes="16x16" href="https://www.graalvm.org/resources/img/favicon/favicon-16x16.png">