Open the playground folder in Sublime or an IDE. You need to edit the .xcplayground extension file within that .playground folder as such where you insert documentation tag right before or after swift code tag.
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<playground version='3.0' sdk='macosx'>
<sections>
<code source-file-name='section-1.swift' hidden="true" />
<documentation relative-path='fragment0.html'/>
<code source-file-name='section-3.swift'/>
<documentation relative-path='fragment11.html'/>
<code source-file-name='section-5.swift'/>
<documentation relative-path='fragment21.html'/>
<code source-file-name='section-7.swift'/>
<documentation relative-path='fragment22.html'/>
<code source-file-name='section-9.swift'/>
<documentation relative-path='fragment23.html'/>
<code source-file-name='section-11.swift'/>
<documentation relative-path='fragment24.html'/>
<code source-file-name='section-13.swift'/>
<documentation relative-path='fragment25.html'/>
<code source-file-name='section-15.swift'/>
<documentation relative-path='fragment26.html'/>
<code source-file-name='section-17.swift'/>
<documentation relative-path='fragment27.html'/>
<code source-file-name='section-19.swift'/>
<documentation relative-path='fragment31.html'/>
<code source-file-name='section-21.swift'/>
<documentation relative-path='fragment32.html'/>
<code source-file-name='section-23.swift'/>
<documentation relative-path='fragment33.html'/>
</sections>
<timeline fileName='timeline.xctimeline'/>
</playground>
The documentation and Swift file and folder structure need to be like this.
