Update themes.md

source/api/themes.md

@@ -2,6 +2,20 @@ title: Themes
 ---
 `hexo.theme` inherits from [Box](box.html), and also saves templates.
 
+{% note warn For theme creators %} In order to show the static site generator behind the web site (like [WAP Analyzer](https://www.wappalyzer.com/)), the best practice would be add the generator meta into HTML head:
+```html
+<meta name="generator" content="Hexo 3.7.1">
+```
+In swig:
+```swig
+<meta name="generator" content="Hexo {{ hexo_version() }}">
+```
+In ejs:
+```ejs
+<meta name="generator" content="Hexo <%= hexo_version() %>">
+```
+{% endnote %}
+
 ## Get a View
 
 ``` js