feat(clipboard): fix clipboard for ssh+tmux

Fix clipboard when attaching to a tmux session
over SSH.

init.lua

@@ -3,6 +3,7 @@ local module_name = "base"
 local utils = require("utils")
 
 local files = {
+    "env",
     "globals",
     "options",
     "autocommands",

lua/core/env.lua

@@ -0,0 +1,4 @@
+-- Tell neovim to prefer tmux as clipboard over xsel/xclip.
+if vim.fn.getenv("TMUX") ~= vim.NIL then
+    vim.fn.setenv("DISPLAY", vim.NIL)
+end