refactor(rules): permit to combine individual rules

The previous rules template set did not permit to combine rules easily
in user jobs.

Using a single hash of individual rules permit to reference them more
clearly. It avoids duplicated conditionnals in the current rules set
and marke it easier to combine them in user jobs, with some
limitations[1].

* templates/Rules.yaml: define the `.rules-map` hash of individual
  rules and reference them in rules templates

* templates/Release/Semantic-release.yaml: use the `.rules-map`
  directly to reduce the conditionnal duplication

Closes #3

Footnotes:
[1]  https://forum.gitlab.com/t/add-conditions-to-rules-array-merged-with-reference/62600