This update for xfce4-genmon-plugin fixes the following issues:

- Update to version 4.3.0
- Update README after switchover to meson
- autotools-build: Explicitly require glib, gtk3
- meson-build: Use shared_module()
- Replace deprecated exo with libxfce4ui 4.21.0
- build: Automate copyright year management
- Add meson build
- autotools-build: Explicitly require libxfce4util
- Fix libxfce4panel include
- Translation Updates