fix: make gha checks (docs, build, etc) triggered by main workflows

[drodarie]

Describe the work done

• Fix release token
• Black, Isort, Build, Docs and API checks can now only be launched by other workflows
• Add a workflow to check commits on branch other than main Regroup the workflows for PR
• Regroup the workflows for the main branch -> renamed into main.yml
• Regroup the workflows for PR -> renamed into pull_request.yml
• Fix README.md
• Update CHANGELOG.md

List which issues this resolves:

closes #873