Proposition to rename "nightly" in another term on the deployment

## Bug description

Currently, the build done on the main/master branch is deployed as "nightly" in different places (web site, download, latest documentation) ex: https://download.eclipse.org/gemoc/packages/nightly/ or https://download.eclipse.org/gemoc/updates/nightly/ or https://download.eclipse.org/gemoc/docs/nightly/

Actually, this isn't done on a daily/nightly basis but on commit on the master branch

For clarity, it would be better to find another name for the folder.

Some proposal:
- `master` (same name as the branch, but the term master isn't politically correct)
- `main` ( politically correct, in the hope we rename oneday the master branch into main)
- `stable` as in our workflow the master branch is considered the stable branch
- `latest_dev` ( a bit less optimistic in the workflow about the quality but closer to the reality )

Any suggestion ?