On the site of lightmaps, the documentation hyperlink redirects to a non-existing url.
It should redirect to one of these websites:
https://developer.playcanvas.com/en/user-manual/graphics/lighting/lightmapping/
https://developer.playcanvas.com/en/user-manual/graphics/lighting/runtime-lightmaps/
Can someone add it to the GitHub issues on the developer.playcanvas.com repo please? I’m off today 
Enjoy your day off @yaustar!
Actually I was wrong, @guzu that is an old blog post not a doc page, most likely the reason why the links to the docs have been updated. Not sure the blog is on github, calling @will in case he wants to update that post.
It may make sense since that post comes up quite often on google search results.
Happy to help! 