Added go.mod file

[whokilleddb]

On latest version of go (go1.25.0 windows/amd64) running go get github.com/fatih/color leads to the error:

go: go.mod file not found in current directory or any parent directory.
        'go get' is no longer supported outside a module.
        To build and install a command, use 'go install' with a version,
        like 'go install example.com/cmd@latest'
        For more information, see https://golang.org/doc/go-get-install-deprecation
        or run 'go help get' or 'go help install'.
 

This is easily fixed by introducing a go.mod file generated using:

go mod init Limelighter

Tested on Windows 24H2 (OS Build 26100.4946)