This is an addon for Minecraft Bedrock edition.
Download the mcpack files from the latest release page. There are two files, for behavior and resource packs.
On most systems Minecraft can now install the packs as soon as you download them or open them. If that doesn’t work, check installation instructions at MCPEDL:
Create a world in Minecraft and make sure you add both the behavior pack and the resource pack.
With this addon, most chickens will occasionally drop random valuable items instead of eggs.