Creeper Backguard Continuation

This is a barebones (re)implementation of Creeper Backguard by JuaanP for the latest version (1.21.8), which makes creepers not explode until within your field of view. It will be archived when/if Creeper Backguard is updated to latest. The mod uses no code from Creeper Backguard but the same idea, so full credit for the idea goes to JuaanP.

Unlike the original Creeper Backguard, it does not check client FOV in singleplayer, instead using a constant 90 FOV horizontally (and 60 vertically) regardless of environment.