terminal: Create module to consolidate term utils

Terminal application, a variety of shell configurations, terminal file
and session management all consolidated in one place.

terminal/.config/zsh/completions/_tmux_attach_start

@@ -0,0 +1,12 @@
+#compdef _tmux_attach_start
+#
+# Requires tmux_attach_start script in path
+#
+# Enables completion for zsh of tmux_attach_start function
+# with currently open sessions, or tmux options.
+
+_tmux_attach_start() {
+  _alternative \
+    "sessions:user sessions:($(tmux list-sessions -F'#{session_name}' 2>/dev/null))"
+}
+