[doc] Add RULES.md

RULES.md

+# Rules on how to contribute
+
+- Definition: protected branches: `master`, `dev`, and other maintenance releases branches
+- Important changes:
+  - A merge request usage is mandatory
+  - Have a review by at least one other contributor (except in the case no contributor are available, for instance, two weeks)
+- minor change: the commit can be directly pushed to `dev`
+- force-push are forbidden on protected branches
+- protected branches should be protected into the repository settings
+- force-push on protected branches exception: solely in case of a secret have been accidentally pushed (i.e.: authentication file, password) that we want to remove from the history by rewriting it.
+- A major release can be done by every contributor (maintainer and developer) through a MR with the endorsement by at least one other contributor