Add Fencyboy v1.3.1

[ScholliYT]

Summary

Add the Fencyboy electric fence sensor (initial add).

Changes

• Initially adds the vendor "Fencyboy" to the device repository
• Initially adds the "Fencyboy" electric fence sensor device with verison v1.3.1 to the device repository
• Documents the standard payload decoder with examples
• Documents the device profile for the Fencyboy v1.3.1

Checklist for Reviewers

• Title and description should be descriptive (Not just a serial number for example).
• profileIDs should not be vendorID and should be a unique value for every profile.
• All devices should be listed in the vendor's index.yaml file.
• Firmware versions can not be changed.
• At least 1 image per device and should be transparent.

Notes for Reviewers

• The device is called "Fencyboy" and the company/vendor is also called "Fencyboy". The validation did not allow this configuration. Hence, I chose to call the device "Fency boy - Electric Fence Sensor". Why is there a limitation like this in the first place? (see "Device name can not contain the vendor name").
• I am adding this device to the repository as part of the LoRaWAN Wall of Fame at The Things Conference 2025 guide.

[CLAassistant]

All committers have signed the CLA.