docs: Add additional external blog posts

This may seem a bit self-indulgent, but both of these features are
either quite new or so old that no one remembers them anymore, so not a
lot of up-to-date content exists for them.

XMonad/Actions/TopicSpace.hs

@@ -103,6 +103,9 @@ import XMonad.Hooks.WorkspaceHistory
 -- display your topics in an historical way using a custom `pprWindowSet'
 -- function. You can also easily switch to recent topics using this history
 -- of last focused topics.
+--
+-- A blog post highlighting some features of this module can be found
+-- <https://tony-zorman.com/posts/topic-space/2022-09-11-topic-spaces.html here>.
 
 -- $usage
 -- You can use this module with the following in your @~\/.xmonad\/xmonad.hs@: