新增：封面嵌入、歌词下载；修复Bug

src/main/utils/mp3Meta.js

@@ -0,0 +1,17 @@
+const NodeID3 = require('node-id3')
+const path = require('path')
+const fs = require('fs')
+const request = require('request')
+const extReg = /^(\.(?:jpe?g|png)).*$/
+
+module.exports = (filePath, meta) => {
+  if (!meta.APIC) return NodeID3.write(meta, filePath)
+  let picPath = path.join(path.dirname(filePath), `${meta.title}-${meta.artist}${path.extname(meta.APIC).replace(extReg, '$1')}`)
+  request(meta.APIC).pipe(fs.createWriteStream(picPath)).on('finish', () => {
+    meta.APIC = picPath
+    NodeID3.write(meta, filePath)
+    fs.unlink(picPath, err => {
+      if (err) console.log(err.message)
+    })
+  })
+}