Turn a script into a tray icon with a menu.

Implements StatusNotifierItem.

1. Write a config file that represents a menu. (See sni-menu.conf.example.)
2. Run sni-menu <conf>. Make it a service if you want.

1. Write a script to dynamically generate the config. (See examples/.)
2. Specifically, fork an sni-menu process and send it a HUP signal to make it reload config. (See examples/weather.sh.)
3. Menu items can communicate back to controller script via any IPC (signals, files, sockets, etc). (See examples/click_count.sh.)

The only requirements are libc and libdbus-1.

$ sudo apt install build-essential pkg-config libdbus-1-dev
$ make