Add the configuration file for merge flow

[f-alizada]

Context

Onboarding new merge flow based on the github actions

Changes Made

Added configuration file the flow was copied from: https://github.com/dotnet/versions/blob/main/Maestro/subscriptions.json. Currently it will not be read or change any behaviour of the merge flow but will be used by the new workflow.

• Documentation https://github.com/dotnet/arcade/blob/main/Documentation/Maestro/New-Inter-Branch-Merge-Approach.md
• One pager: https://github.com/dotnet/dnceng/blob/main/Documentation/OnePagers/github-action-inter-branch-merge.md

Testing

None -> it is not functionality related changes

Notes

The flow from vs17.7 to vs17.8 was not added to the new configuration since the sdk 7 release has reached end of life.

FYI: @pavelsavara , @mmitche

[pavelsavara]

@f-alizada I think you could also add the actual workflow trigger to main branch, because next time a release branch would be branched, the workflow trigger file would be already there.

[f-alizada]

@f-alizada I think you could also add the actual workflow trigger to main branch, because next time a release branch would be branched, the workflow trigger file would be already there.

This is good, however I would like to bring this file from the merge flow => we will not see any conflicting files from the latest release -> main.