Onboard to Arcade dependency flow

[dtivel]

https://github.com/dotnet/arcade/blob/main/Documentation/DependencyFlowOnboarding.md

[pjcollins]

I added a subscription with weekly cadence to flow arcade into this repo via:

darc add-subscription --channel ".NET Eng - Latest" --source-repo "https://github.com/dotnet/arcade" --target-repo https://github.com/dotnet/sign

...

https://github.com/dotnet/arcade (.NET Eng - Latest) ==> 'https://github.com/dotnet/sign' ('main')
  - Id: 8f57acfa-4ace-4305-9a3e-93d7b3f76a0c
  - Update Frequency: EveryWeek
  - Enabled: True
  - Batchable: False
  - Excluded Assets: []
  - PR Failure Notification tags: 
  - Source-enabled: False
  - Merge Policies: []
  - Last Build: 20250801.2 (40693ae2ee51e447f6ca96d07bc1ba779dcb9b9c)

We should hopefully see an automated update here next week!