waybar nix flake installation instructions

[guttermonk]

Need instructions for installing the waybar nix flake added to the wiki.

I'm sure I'm doing something wrong, as I'm getting the following error, just can't figure out what's causing it.

error: builder for '/nix/store/rs802zh6r076kvryn01ycfr42fy8afkx-home-manager-path.drv' failed with exit code 25;
       last 1 log lines:
       > error: collision between `/nix/store/z683jv87dpfr5gc8ypkhngzbgkbkn4gf-waybar-0.10.3/include/cava/config.h' and `/nix/store/70pp4bsi43jwzgjw0f84hcj9vxpr95ah-waybar-0.11.0+date=2024-10-25_5f26051/include/cava/config.h'
       For full logs, run 'nix log /nix/store/rs802zh6r076kvryn01ycfr42fy8afkx-home-manager-path.drv'.
error: 1 dependencies of derivation '/nix/store/im4gj17yh1p0lmhnqnv35141vja0v2hb-home-manager-generation.drv' failed to build