Add availability to default metafields

Change-Id: If635703e66995fd11d6d2ed0326fe38da96de98a
diff --git a/dev/js/src/vc/array.js b/dev/js/src/vc/array.js
index 8a47a3d..1c01955 100644
--- a/dev/js/src/vc/array.js
+++ b/dev/js/src/vc/array.js
@@ -3,6 +3,7 @@
     // layerInfo                   // stored
     // tokenSource                 // stored
     ['author', 'text'],            // text
+    ['availability', 'string'],    // string
     // ['biblEditionStatement', 'string'], // stored
     ['corpusAuthor', 'text'],      // text
     // ['corpusEditor', 'string'], // stored