CONTRIBUTING: Restore link to dev/git/README.md document
CONTRIBUTING: Restore link to dev/git/README.md document

The Documentation/dev/git/README.md document is the main dispatch
point for documentation of VTK Git infrastructure.  We should
link to it from the contribution guidelines document.

sumedhasingla/VTK,gram526/VTK,gram526/VTK,jmerkow/VTK,mspark93/VTK,keithroe/vtkoptix,sumedhasingla/VTK,sumedhasingla/VTK,gram526/VTK,candy7393/VTK,jmerkow/VTK,SimVascular/VTK,gram526/VTK,SimVascular/VTK,msmolens/VTK,msmolens/VTK,gram526/VTK,sumedhasingla/VTK,sankhesh/VTK,SimVascular/VTK,demarle/VTK,candy7393/VTK,sankhesh/VTK,demarle/VTK,keithroe/vtkoptix,msmolens/VTK,mspark93/VTK,sankhesh/VTK,jmerkow/VTK,candy7393/VTK,sankhesh/VTK,sumedhasingla/VTK,keithroe/vtkoptix,keithroe/vtkoptix,sumedhasingla/VTK,candy7393/VTK,mspark93/VTK,jmerkow/VTK,SimVascular/VTK,sankhesh/VTK,keithroe/vtkoptix,keithroe/vtkoptix,jmerkow/VTK,mspark93/VTK,sankhesh/VTK,msmolens/VTK,jmerkow/VTK,sumedhasingla/VTK,demarle/VTK,candy7393/VTK,SimVascular/VTK,candy7393/VTK,candy7393/VTK,mspark93/VTK,mspark93/VTK,msmolens/VTK,SimVascular/VTK,SimVascular/VTK,gram526/VTK,candy7393/VTK,msmolens/VTK,mspark93/VTK,gram526/VTK,msmolens/VTK,demarle/VTK,msmolens/VTK,sankhesh/VTK,demarle/VTK,keithroe/vtkoptix,keithroe/vtkoptix,gram526/VTK,mspark93/VTK,SimVascular/VTK,jmerkow/VTK,demarle/VTK,sumedhasingla/VTK,demarle/VTK,sankhesh/VTK,demarle/VTK,jmerkow/VTK