Changed package name and switched to using gradle variables in mod.json

[BrailleBennett]

Right now, your package name of "net.chatsounds" is wrong, and is against the java standard for package names. In fact, the domain chatsounds.net isn't even registered, which poses a risk to the project. This PR renames the mod package to properly follow the accepted standard for packages hosted on GitHub. Additionally, I changed to use the gradle.properties variables in the fabric.mod.json file, as I noticed you forgot to update the data in that file when updating the mod to 1.21.4.

[AlurienFlame]

Yeah, okay. Bit micromanagey but I see the rationale for the changes. I had been avoiding updating the requirements because I wanted to avoid a situation (which I've encountered before) where people want to use versions of dependencies that will technically work, but are earlier than the versions I developed on. This way errs on the side of preventing the game from ever crashing, but at the cost of making it more likely that fabric will prevent it from launching it at all because it thinks the versions aren't compatible.