feat(icon): register favicon.ico when available (#258)

lib/meta/module.js

@@ -1,3 +1,5 @@
+const { join } = require('path')
+const { existsSync } = require('fs')
 const { find, isUrl } = require('../utils')
 
 module.exports = function nuxtMeta (pwa) {
@@ -96,6 +98,13 @@ function generateMeta (pwa) {
     }
   }
 
+  const favicon = join(this.options.srcDir, this.options.dir.static, 'favicon.ico')
+  if (options.favicon && !find(this.options.head.link, 'rel', 'shortcut icon') && existsSync(favicon)) {
+    console.warn('You are using a low quality icon, use icon png. See https://pwa.nuxtjs.org/modules/icon.html')
+
+    this.options.head.link.push({ rel: 'shortcut icon', href: 'favicon.ico' })
+  }
+
   // Title
   if (options.name && !this.options.head.title && typeof this.options.head.titleTemplate !== 'function') {
     this.options.head.title = options.name