Add option to force switch monitor.

[itlki]

display-switch/src/display_control.rs

Line 53 in c8458c5

if raw_source.value() & 0xff == input.value() {

This line prevents me to switch one of my monitor because it reports wrong input source. It would be a nice to have feature when run with a flag such as display-switch --force-switch, the code doesn't rely on the input source and force monitor to switch.