Tag meta not updated

[clarkwinkelmann]

In the latest version I added the ability to set tags on new discussions.

For now I have skipped adding the meta update code for tags for simplicity. I'll add it if there's demand.

I'm unsure of the performance hit if tag meta is updated together with the random tags option with a large number of tags, but for when manually selecting a tag the performance impact must be negligible since it will happen just once at the end of the seeder.

Please do not submit a PR, it's a simple addition, it will likely take me more time to review a PR compared to implementing it myself.