waypipe: fix border drawing when compositor has output scaling != 1

[Mic92]

The old version did break if a screen used output scaling (i.e. on 200% scaling on 4k screens) by making the border only a quarter of the needed size. This was fixed by requesting the compositor output scaling.

I found this bug when I tested this patch prior to upstreaming the patch to https://gitlab.freedesktop.org/mstoeckl/waypipe/-/merge_requests/21

I also updated the manpage

Description of changes

Checklist for things done

• [x] Summary of the proposed changes in the PR description
• [ ] More detailed description in the commit message(s)
• [ ] Commits are squashed into relevant entities - avoid a lot of minimal dev time commits in the PR
• [ ] Contribution guidelines followed
• [ ] Ghaf documentation updated with the commit - https://tiiuae.github.io/ghaf/
• [ ] PR linked to architecture documentation and requirement(s) (ticket id)
• [ ] Test procedure described (or includes tests). Select one or more:
  • [ ] Tested on Lenovo X1 x86_64
  • [ ] Tested on Jetson Orin NX or AGX aarch64
  • [ ] Tested on Polarfire riscv64
• [ ] Author has run nix flake check --accept-flake-config and it passes
• [ ] All automatic Github Action checks pass - see actions
• [ ] Author has added reviewers and removed PR draft status

Testing

[Mic92]

I just got pinged that the new approach will look differently: https://gitlab.freedesktop.org/mstoeckl/waypipe/-/merge_requests/20 Anyway, until this is implemented this patch will be slightly more correct.