fix: add ARTIFACT rarity to magic items rarity enum

[techwraith]

What does this do?

This PR fixes the issue that when quering the API using GraphQL for Magic Items and there is a magic Item with Common Rarity, the API return a 500 response because there no "ARTIFACT" rarity listed on the enum for the GraphQL.

How was it tested?

Using the Apollo sandbox explorer perform the following query with the following Variables:
Query:

query MagicItemsQuery($equipmentCategory: StringFilter, $order: MagicItemOrder) {
  magicItems(equipment_category: $equipmentCategory, order: $order) {
    index
    name
    desc
    rarity
    equipment_category {
      index
      name
    }
  }
}

Is there a Github issue this is resolving?

#331 (ish)

Was any impacted documentation updated to reflect this change?

N/A

Here's a fun image for your troubles

[bagelbits]

I forgot that Artifact is also a rarity.

[github-actions]

🎉 This PR is included in version 2.5.2 🎉

The release is available on GitHub release

Your semantic-release bot 📦🚀

[techwraith]

Thanks @bagelbits!

[bagelbits]

Just doing my job.