feat: allow turning the beep on boot off

[dahlb]

I'm new to esphome but I'm am trying to prevent the tag reader from beeping when the power goes out. There is a comment about a condition that seems to have been removed, using the state of the buzzer but that didn't seem to be available when I tried to reference it during startup. This works and allows me to continue tracking any other updates from this package while overriding it locally with substitutions.

ie

substitutions:
  name: "tagreader-playroom"
  friendly_name: "tagreader-playroom"
  beep_on_boot: "false"

[bjebb]

I would love this feature, the boot-beep is disturbing.