update tmux configuration

.tmux.conf

@@ -1 +1,14 @@
-set -g default-terminal "xterm-256color"
+# Use C-j as secondary prefix key
+set -g prefix2 C-j
+
+# Send C-j when C-j C-j is pressed
+bind-key C-j send-prefix -2
+
+set -g default-terminal screen-256color
+
+# Use vi-style key bindings in view-mode, tree-mode, etc.
+#set -g mode-keys vi
+
+# enable activity alerts
+setw -g monitor-activity on
+set -g visual-activity on