refactor: load theme/enhanceApp.js instead of index.js

lib/prepare.js

@@ -63,10 +63,18 @@ if (!Object.assign) Object.assign = require('object-assign')`
 
   // 6. handle enhanceApp.js
   const enhanceAppPath = path.resolve(sourceDir, '.vuepress/enhanceApp.js')
-  writeEnhanceTemp('enhanceApp.js', enhanceAppPath, fs.existsSync(enhanceAppPath))
+  writeEnhanceTemp(
+    'enhanceApp.js',
+    enhanceAppPath,
+    fs.existsSync(enhanceAppPath)
+  )
 
-  // 7. handle the theme index.js
-  writeEnhanceTemp('themeEnhanceApp.js', options.themeApp, fs.existsSync(options.themeApp))
+  // 7. handle the theme enhanceApp.js
+  writeEnhanceTemp(
+    'themeEnhanceApp.js',
+    options.themeEnhanceAppPath,
+    fs.existsSync(options.themeEnhanceAppPath)
+  )
 
   return options
 }
@@ -167,9 +175,9 @@ async function resolveOptions (sourceDir) {
       options.notFoundPath = path.resolve(__dirname, 'default-theme/NotFound.vue')
     }
 
-    const themeApp = path.resolve(themeDir, 'index.js')
-    if (fs.existsSync(themeApp)) {
-      options.themeApp = themeApp
+    const themeEnhanceAppPath = path.resolve(themeDir, 'index.js')
+    if (fs.existsSync(themeEnhanceAppPath)) {
+      options.themeEnhanceAppPath = themeEnhanceAppPath
     }
   }