Import Geant4 10.7.1 source tree

CONTRIBUTING.rst

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+Contributing to Geant4
+=====
+To contribute patches to Geant4, users can submit Pull Requests (PR) such that:
+
+- A single PR refers to a single particular topic (fix or suggested enhancement);
+  PRs including uncorrelated changes in codes in different areas or modules will
+  not be considered.
+
+A PR will be examined by a responsible and eventually extracted for a patch in
+the development repository of Geant4, to be included in a future release or
+patch.
+
+For simple bug-fixes, it is anyhow recommended to use the official
+Bugzilla problem reporting system.
+- Problem reports: `Bugzilla problem reporting system <https://bugzilla-geant4.kek.jp>`_.
+- User Forum: `Geant4 Forum <https://geant4-forum.web.cern.ch>`_.
+- Documentation: `User Documentation <https://cern.ch/geant4/support/user_documentation>`_.
+
+The Geant4 Collaboration