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

* templates/Release/Semantic-release.yaml: use
  `semantic-release-gitlab` image.

Create new release when merge requests are merged into the
`$STABLE_BRANCH` branch.

* templates/Release/Semantic-release.yaml: run `semantic-release` with
  the latest EOLE container for `$STABLE_BRANCH` branch if one of its
  configuration is present.

* .gitlab-ci.yml: execute a new stage `release` for
  `semantic-release`.

* release.config.js: create `docs/CHANGELOG.md` and publish new
  releases on Gitlab.
  Mangle commits to have links for users, issues and commits id.

* release-rules.js: create semantic version update rules based on
  `docs/CONTRIBUTING.md`.