Explicitly define action permissions

[xPaw]

I changed org defaults to not have read/write, so I think it's gonna need these perms now:

permissions:
  contents: read
  packages: write

[williamboman]

Is contents: read ever needed on public repos? I'm curious, GitHub docs tell absolutely nothing.

[xPaw]

Github docs are terrible for permissions, it's probably not needed because it should be default, but I list it to be explicit in the used permissions.