fix some problems and An interesting feature has been added

[jinzhongjia]

Fixed problems：

• When the meta tag about image in the layout page is set to empty, it will still appear in the generated file
• In the layout page, the introduction of the search page is added, and some JS that do not need to be loaded immediately are changed to defer

  New feature:

  the "search" feature! However, to use this feature, you need to install the hexo Generator Search plug-in It is to retrieve articles by requesting json files generated by plug-ins I added a logical judgment to the layout.ejs file not to trigger the Search function in the generated page when the Hexo Generator Search plug-in is not configured, that means It also does not load the JS file used for the search

One problem is that the current JS files are small and separate, which causes multiple requests to be made when accessing the browser. This problem will be magnified when communicating over HTTP 1.1. I think I may merge a few of these JS files in the future

[jinzhongjia]

oh,and CSS file is the same

[adisaktijrs]

Awesome!!

I think I need to update the documentation page and move it to the repo README.md (so every contributor can add new feature usage/updates directly on it) since currently the doc page is located on my personal blog😅