Add tmux config and replace zellij with tmux in zshrc.

Zhrc also has some light refactoring, and has added a zsh local file
which gets sourced if it exists, useful for adding local environment
variables

home/.config/tmux/tmux-move-pane.sh

@@ -0,0 +1,14 @@
+#!/bin/zsh
+
+source_pane=$(tmux display-message -p '#{pane_id}')
+target_window=$1
+
+window_exists=$(tmux list-windows -F '#I' | grep "^$target_window$")
+
+if [ -z "$window_exists" ]; then
+    tmux break-pane -d -t $target_window
+else
+    target_pane=$(tmux list-panes -t $target_window -F '#{pane_id}' | sort | tail -n 1)
+    tmux join-pane -d -s $source_pane -t $target_pane
+    tmux select-layout -t $target_window main-vertical
+fi