vweb.tmpl: update README.md with @js directive (#7791)

vlib/vweb/tmpl/README.md

@@ -108,6 +108,19 @@ Project root
 ```
 > Note that there shouldn't be a file suffix,
     it is automatically appended and only allows `html` files.
+    
+    
+## js
+The js directive consists of two parts, the `@js` tag and `'<path>'` string,
+where you can insert your src
+```
+@js '<url>'
+```
+
+### Example
+```html
+@js 'myscripts.js'
+```
 
 # Variables
 All variables which are declared before can be used through the `@{my_var}` syntax.