fix: pages number in the pagination plugin (#963)

Author: martinsotirov

packages/@vuepress/plugin-pagination/index.js

@@ -1,8 +1,8 @@
 const { path } = require('@vuepress/shared-utils')
 
 function getIntervallers (max, interval) {
-  const count = Math.floor(max / interval)
-  const arr = [...Array(count + 1)]
+  const count = max % interval === 0 ? Math.floor(max / interval) : Math.floor(max / interval) + 1
+  const arr = [...Array(count)]
   return arr.map((v, index) => {
     const start = index * interval
     const end = (index + 1) * interval - 1