Improve documentation for custom_card_imswel_person

[rst-ack]

Is your enhancement request related to a problem? Please describe.
The documentation for custom_card_imswel_person is seemingly missing details or examples for the ulm_card_imswel_person_findmy_script, ulm_card_imswel_person_gps_tracker, and ulm_card_imswel_person_wifi_tracker variables.

Describe the solution you'd like
The examples in the variables table show example entities to use for the variables, however, in particular for the ulm_card_imswel_person_findmy_script variable, I think it would be helpful to provide a link (in the Explanation column) to somewhere that can guide the user on creating a script to make the phone ring. Being able to do this might be assumed knowledge to use ULM, but if this is the case I feel it might be worth calling it out.