ci: update workflows and github token permissions

[tbouffard]

• create-release.yml: add a comment to explain why the write permission is set
• create-tag.yml: remove permission declaration as we use a PAT to create the tag
• publish-online-example.yml: push to the gh-pages branch

Notes

This PR applies to this repository the same configuration as we already did for documentation content repositories: see https://github.com/bonitasoft/bonita-documentation-site/issues/443. See also https://github.com/bonitasoft/bonita-documentation-site/pull/579

Documentation of the actions whose permissions changed

• https://github.com/anothrNick/github-tag-action
• https://github.com/ncipollo/release-action
• https://github.com/peaceiris/actions-gh-pages

[sonarcloud[bot]]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

No Coverage information
No Duplication information