Use the tmux-sessionizer from GitHub

Use the tmux-sessionizer code from GitHub instead of writing it myself
and apply a patch to change the directories it uses to provide
suggestions.

nix/pkgs/tmux-sessionizer/configure-directories.patch

@@ -0,0 +1,15 @@
+diff --git a/tmux-sessionizer b/tmux-sessionizer
+index fa1bec5..4d79e0b 100755
+--- a/tmux-sessionizer
++++ b/tmux-sessionizer
+@@ -22,9 +22,7 @@ hydrate() {
+ if [[ $# -eq 1 ]]; then
+     selected=$1
+ else
+-    # If someone wants to make this extensible, i'll accept
+-    # PR
+-    selected=$(find ~/ ~/personal ~/personal/dev/env/.config -mindepth 1 -maxdepth 1 -type d | fzf)
++    selected=$(find -L ~/ ~/Code ~/Documents -mindepth 1 -maxdepth 1 -type d | sort | fzf)
+ fi
+ 
+ if [[ -z $selected ]]; then