document permissions for ghp wf

[cfhaak]

`remote: Permission to someone/dse-static-test.git denied to github-actions[bot].

fatal: unable to access 'https://github.com/someone/dse-static-test.git/': The requested URL returned error: 403

Error: Action failed with "The process '/usr/bin/git' failed with exit code 128" `

Even though this error is expected to happen under default settings it would be of great help for new users if the correct settings for the repo would be hinted in the docs. -> Set "Setting – Actions – General – Workflow Permissions" to "Read & Write Permissions".

[csae8092]

I think this can be closed as the new gh-action worfklow file build.yml

• does not use gh-pages branch any more
• sets some permissions

  # Sets permissions of the GITHUB_TOKEN to allow deployment to GitHub Pages
  permissions:
  contents: read
  packages: write
  pages: write
  id-token: write