This commit adds support for auto completion for bash and zsh
shells. A new root level command called "completion" has been
introduced, and the user can get the auto completion code by
running `ark completion bash/zsh`.
For bash completion, the built-in GenBashCompletion() from cobra
has been used, but for zsh, the built-in GenZshCompletion() is
known to cause issues. The workaround has been copied from zsh
completion code of kubectl.
Signed-off-by: Shubham <shubham@linux.com>
Shubham Minglani