Fix search context to only search 2.x docs (#39)

Author: jbrooksuk

.vuepress/theme/index.js

@@ -0,0 +1,9 @@
+module.exports = {
+    extend: '@vuepress/theme-default',
+
+    plugins: [
+        ['@vuepress/search', {
+            test: ['/2\.x/'],
+        }]
+    ],
+}