update switcher_webpapi.md

[ygarti]

i think you forgot to define the automation on the input select change.
you have made the script switcher_turn_on_timer_script but you never use it

[dmatik]

No need for any automation.
Please note that in my use changing the input select value not supposed to trigger anything, but there is a script to turn the switcher with timer and that script is using the current value from that input select. I have a button in my UI which calls that script.
Of course if you want to trigger the timer on every input select change in your configuration, you can do an automation for that.