Add game config admin API docs

[tudddorrr]

New game config admin docs

• Added content/docs/1.x/admin/game-config-api.mdx, covering how to read and update live config through the admin API and schedule future changes
• Documented the required scopes: read:gameConfig for reading, and write:gameConfig for updating config and managing scheduled changes
• Added Prop and ScheduledGameConfigChange type references, noting that a null value deletes a prop when a scheduled change is applied

Navigation and cross-references

• Registered the new page in content/docs/1.x/admin/meta.json
• Updated the Bruno collection page to list Game config requests alongside Leaderboards and Stats

Bruno collection

• Added a Game config folder and request to the embedded public/bruno-collection.html so the exported collection matches the documented admin endpoints