Update jquery v3.3.1 to v3.4.0 (mmistakes#2129)

* Update jquery v3.3.1 to v3.4.0
* Update `main.min.js`

Close mmistakes#2127

Author: torrocus

assets/js/main.min.js

@@ -18,7 +18,7 @@ minimal mistakes
 |  |  |   └── jquery.smooth-scroll.min.js  # make same-page links scroll smoothly
 |  |  ├── vendor
 |  |  |   └── jquery
-|  |  |       └── jquery-3.3.1.min.js
+|  |  |       └── jquery-3.4.0.min.js
 |  |  ├── _main.js                         # jQuery plugin settings and other scripts
 |  |  └── main.min.js                      # concatenated and minified scripts
 ```

assets/js/vendor/jquery/jquery-3.3.1.min.js

@@ -26,7 +26,7 @@
     "uglify-js": "^3.4.9"
   },
   "scripts": {
-    "uglify": "uglifyjs assets/js/vendor/jquery/jquery-3.3.1.min.js assets/js/plugins/jquery.fitvids.js assets/js/plugins/jquery.greedy-navigation.js assets/js/plugins/jquery.magnific-popup.js assets/js/plugins/jquery.ba-throttle-debounce.js assets/js/plugins/smooth-scroll.js assets/js/plugins/gumshoe.js assets/js/_main.js -c -m -o assets/js/main.min.js",
+    "uglify": "uglifyjs assets/js/vendor/jquery/jquery-3.4.0.min.js assets/js/plugins/jquery.fitvids.js assets/js/plugins/jquery.greedy-navigation.js assets/js/plugins/jquery.magnific-popup.js assets/js/plugins/jquery.ba-throttle-debounce.js assets/js/plugins/smooth-scroll.js assets/js/plugins/gumshoe.js assets/js/_main.js -c -m -o assets/js/main.min.js",
     "add-banner": "node banner.js",
     "watch:js": "onchange \"assets/js/**/*.js\" -e \"assets/js/main.min.js\" -- npm run build:js",
     "build:js": "npm run uglify && npm run add-banner"