Integrate improved GraphQL Docs

Created by: billCaplan

Describe the issue

We do not have a specific page to point users to that describes our GraphQL API that lives outside the product.

Where is the issue located?

Schema doc should probably be linked from here: https://docs.sourcegraph.com/api/graphql

Suggested resolution

• Complete GitHub Action
• Complete SpectaQL Properties File
• Upload Action to SG Org
• Add to relevant repo
• Ensure the file updates as intended