Revert "nvim: init: Drop tmux configuration for copying to system clipboard"

This reverts commit c37bd7d451.

Copying to system clipboard seems to have broken again and need to
revert this.

See https://github.com/neovim/neovim/issues/21636.

nvim/.config/nvim/init.lua

@@ -74,6 +74,20 @@ vim.g.matchup_surround_enabled     = 1
 -- textobj-word-column
 vim.g.textobj_wordcolumn_no_default_key_mappings = 1
 
+-- See :help clipboard and https://github.com/neovim/neovim/issues/14545
+vim.g.clipboard = {
+  name = "tmux",
+  copy = {
+    ["+"] = "tmux load-buffer -w -",
+    ["*"] = "tmux load-buffer -w -"
+  },
+  paste = {
+    ["+"] = "tmux save-buffer -",
+    ["*"] = "tmux save-buffer -"
+  },
+  cache_enabled = true
+}
+
 -- No default mappings for tmux navigator
 vim.g.tmux_navigator_no_mappings    = 1
 -- Write the current buffer, but only if changed before navigating from Vim to tmux pane