feat(semantic-release): don't build changelog on prerelease branches

feat(semantic-release): don't build changelog on prerelease branches

By default, semantic-release build changelog even for prerelease branches which looks like duplicated entries to users.

Use a workaround to avoid changelog generation for prerelease branches by building the configuration in several steps instead of a direct module.exports at the top.

There are no effect on this project since the branches configuration attribute only contains stable but can be used for other project with the only change to declare prerelease branches.

• release.config.js: rework the configuration file to conditionnally execute @semantic-release/changelog and add its assets to the git plugin.