Use tmux clipboard provider on Wayland

On Gnome Shell on Wayland `wl-copy` is automatically detected but using
it requires switching focus to the temporary invisible window it creates
as a workaround to the Wayland security feature that only the focused
application can interact with the clipboard. This does not happen when
`nvim` is run outside of `tmux`, so I can only assume that `tmux` is
seen to be the focused application, even though it's running inside
`kitty`, rather than `nvim` when running inside `tmux`.

plugin/settings.lua

@@ -3,6 +3,10 @@ vim.g.loaded_node_provider = 0
 vim.g.loaded_perl_provider = 0
 vim.g.loaded_ruby_provider = 0
 
+if vim.env.TMUX ~= nil and vim.env.WAYLAND_DISPLAY ~= nil then
+  vim.g.clipboard = "tmux"
+end
+
 -- Keep cursor from buffer edges
 vim.opt.sidescrolloff = 5