tmux: add 'focusEvents'

With `tmux-sensible` being disabled by default, add an easy toggle to
enable this functionality.

Disabled by default, as in upstream `tmux`.

tests/modules/programs/tmux/default-shell.conf

@@ -19,6 +19,7 @@ set -g mode-keys   emacs
 
 
 set  -g mouse             off
+set  -g focus-events      off
 setw -g aggressive-resize off
 setw -g clock-mode-style  12
 set  -s escape-time       500

tests/modules/programs/tmux/disable-confirmation-prompt.conf

@@ -19,6 +19,7 @@ bind-key -N "Kill the current pane" x kill-pane
 
 
 set  -g mouse             off
+set  -g focus-events      off
 setw -g aggressive-resize off
 setw -g clock-mode-style  12
 set  -s escape-time       500

tests/modules/programs/tmux/emacs-with-plugins.conf

@@ -19,6 +19,7 @@ set -g mode-keys   emacs
 
 
 set  -g mouse             off
+set  -g focus-events      off
 setw -g aggressive-resize on
 setw -g clock-mode-style  24
 set  -s escape-time       500

tests/modules/programs/tmux/mouse-enabled.conf

@@ -17,6 +17,7 @@ set -g mode-keys   emacs
 
 
 set  -g mouse             on
+set  -g focus-events      off
 setw -g aggressive-resize off
 setw -g clock-mode-style  12
 set  -s escape-time       500

tests/modules/programs/tmux/prefix.conf

@@ -22,6 +22,7 @@ bind -N "Send the prefix key through to the application" \
 
 
 set  -g mouse             off
+set  -g focus-events      off
 setw -g aggressive-resize off
 setw -g clock-mode-style  12
 set  -s escape-time       500

tests/modules/programs/tmux/shortcut-without-prefix.conf

@@ -23,6 +23,7 @@ bind C-a last-window
 
 
 set  -g mouse             off
+set  -g focus-events      off
 setw -g aggressive-resize off
 setw -g clock-mode-style  12
 set  -s escape-time       500

tests/modules/programs/tmux/vi-all-true.conf

@@ -19,6 +19,7 @@ set -g mode-keys   vi
 
 
 set  -g mouse             off
+set  -g focus-events      off
 setw -g aggressive-resize on
 setw -g clock-mode-style  24
 set  -s escape-time       500