you can set the appleTV to send audio to the HomePod via airplay.
One big thing to keep in mind, The TV's built in apps, and other external devices like a cable box or blu-ray player will not be able to use the HomePod. Depending on your use, this could be a big issue.
I highly recommend against this though.
it requires a very stable wifi connection to work well. which depending on where it is in your house can be problematic.
it sometimes disconnects,
Different apps on the aTV vary as to how well they handle airplay, and it can lead to delays, either in the audio/video sync, or in the time it takes things to happen - "press play -> -> wait 2-3 seconds while it syncs up to HomePod -> -> aTV actually starts playing"
a cable is a much more solid connection, with far fewer points of failure.