Re-export express for plugins

typings/pluginapi.d.ts

@@ -78,6 +78,15 @@ import * as express from "express"
  * ]
  */
 
+/**
+ * The Express import used by code-server.
+ *
+ * Re-exported so plugins don't have to import duplicate copies of Express and
+ * to avoid potential version differences or issues caused by running separate
+ * instances.
+ */
+export { express }
+
 /**
  * Use to add a field to a log.
  *