[DO NOT MERGE] Add initial merge flow file

[f-alizada]

Context

Introducation of the merge flow.

Changes Made

Added the github workflow (actions) which will be executed on push changes into the vs1** branches and will automatically create upstream merge request.

Testing

Testing was done manually: https://github.com/f-alizada/msbuild/actions

Should be merged only after this: https://github.com/dotnet/msbuild/pull/10257 is merged