cmd: introduce subcommands for gokakashi

[scriptnull]

Introducing different commands in gokakashi binary.

Needed for #20

default command

This prints the help message.

$ docker run --rm gokakashi:dev.1 
GoKakashi - The Container image vulnerability management platform

Usage:
  gokakashi [flags]
  gokakashi [command]

Available Commands:
  completion  Generate the autocompletion script for the specified shell
  help        Help about any command
  scan        Scan a container image
  server      Start the GoKakshi Server
  version     Print version

Flags:
  -h, --help   help for gokakashi

Use "gokakashi [command] --help" for more information about a command.

server command

$ docker run --rm gokakashi:dev.1 server
2024/10/18 00:10:21 === Starting goKakashi Tool ===
2024/10/18 00:10:21 Please provide the path to the config YAML file using --config

Why goKakashi to gokakashi?

Now that gokakshi can be accessed and used as a binary, people tend to ignore casing while typing commands. Hence made it to be all small letters.