Adding campaign events extension to pixel

[vaughnwalters]

Adding the Campaign Events extension to the pixel list of repositories. The repo successfully clones into pixel and I am able to open the extension from local port 3000

[nicholasray]

Looks great @vaughnwalters !

The only thing I noticed is that because the CampaignEvents extension reportedly adds tables the database, we'll want to update the seed data that Pixel uses in this PR as well.

I've already followed the steps in https://github.com/wikimedia/pixel-seed-data to add the new file, all that is left is to change the following line in Dockerfile.database to:

ARG database="database_2023-01-27_13-42-07-0700(MST).tar.gz"

After that, I think it's good to go!

[vaughnwalters]

Ah, okay thank you for that! I wasn't sure if it meant to update that pixel seed data repo if there was data added to the DB, or if there were schema changes. I just pushed the updated line to the Dockerfile.database file to this PR