fix(plugin): add missing $ prefix to globalName (#356)

Author: ricosmall

lib/plugin.js

@@ -2,7 +2,7 @@ import Axios from 'axios'
 import defu from 'defu'
 <% if (options.retry) { %>import axiosRetry from 'axios-retry'<% } %>
 
-const globalName = '<%= globalName %>'
+const globalName = '$<%= globalName %>'
 
 // Axios.prototype cannot be modified
 const axiosExtra = {