various nvim/tmux updates

* make sure diffs open vertically in vim
* update tmux theme
* allow tmux to change the title of the terminal
* add .nvim/shada to gitignore ?

tmux/tmux.conf.symlink

@@ -41,8 +41,8 @@ bind = select-layout tiled
 set -g base-index 1
 setw -g pane-base-index 1
 
-# set-option -g set-titles on
-# set-option -g set-titles-string "#T - #W"
+set-option -g set-titles on
+set-option -g set-titles-string "#T - #W"
 # set-window-option -g automatic-rename on
 
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