feat(search-plugin): add namespace option (#706)

Ref: docsifyjs/docsify@28beff8

Author: SidVal

plugins.md

@@ -39,7 +39,13 @@ By default, the hyperlink on the current page is recognized and the content is s
       },
 
       // Headline depth, 1 - 6
-      depth: 2
+      depth: 2,
+
+      hideOtherSidebarContent: false, // whether or not to hide other sidebar content
+
+      // To avoid search index collision
+      // between multiple websites under the same domain
+      namespace: 'website-1',
     }
   }
 </script>
@@ -190,4 +196,4 @@ Provided by [@jhildenbiddle](https://github.com/jhildenbiddle/docsify-tabs).
 
 ## More plugins
 
-See [awesome-docsify](/es/awesome?id=plugins)
+See [awesome-docsify](/es/awesome?id=plugins)