docs: Improve embed files code fragment (docsifyjs#2650)

Author: jacobsorme

docs/embed-files.md

@@ -65,9 +65,21 @@ Sometimes you don't want to embed a whole file. Maybe because you need just a fe
 ```
 
 In your code file you need to surround the fragment between `/// [demo]` lines (before and after the fragment).
-Alternatively you can use `### [demo]`. By default, only identifiers are omitted. To omit the entire line containing the identifier in the fragment output, you can add the `:omitFragmentLine` option.
+Alternatively you can use `### [demo]`. By default, only identifiers are omitted. To omit the entire line containing the identifier in the fragment output, add the `:omitFragmentLine` option. This is useful if your code fragment is e.g. HTML and you want to hide the Docsify fragment identifier from showing in your HTML source. `<!-- /// [demo] -->` in your source file and `:omitFragmentLine` will make the `-->` not show up in your Docsify code fragment section.
 
-Example:
+Example: In the source file \_media/example.js, `/// [demo]` identifiers have been included:
+
+```markdown
+[filename](_media/example.js ':include :type=code')
+```
+
+[filename](_media/example.js ':include :type=code')
+
+Adding the `:fragment=demo` results in the following:
+
+```markdown
+[filename](_media/example.js ':include :type=code :fragment=demo')
+```
 
 [filename](_media/example.js ':include :type=code :fragment=demo')