add auto-completion doc for karmadactl

Signed-off-by: lonelyCZ <531187475@qq.com>

docs/bash-auto-completion-on-linux.md

@@ -0,0 +1,47 @@
+# bash auto-completion on Linux
+## Introduction
+The karmadactl completion script for Bash can be generated with the command karmadactl completion bash. Sourcing the completion script in your shell enables karmadactl autocompletion.
+
+However, the completion script depends on [bash-completion](https://github.com/scop/bash-completion), which means that you have to install this software first (you can test if you have bash-completion already installed by running `type _init_completion`).
+
+## Install bash-completion
+bash-completion is provided by many package managers (see [here](https://github.com/scop/bash-completion#installation)). You can install it with `apt-get install bash-completion` or `yum install bash-completion`, etc.
+
+The above commands create `/usr/share/bash-completion/bash_completion`, which is the main script of bash-completion. Depending on your package manager, you have to manually source this file in your `~/.bashrc` file.
+
+```bash
+source /usr/share/bash-completion/bash_completion
+```
+
+Reload your shell and verify that bash-completion is correctly installed by typing `type _init_completion`.
+
+## Enable karmadactl autocompletion
+You now need to ensure that the karmadactl completion script gets sourced in all your shell sessions. There are two ways in which you can do this:
+
+- Source the completion script in your ~/.bashrc file:
+
+```bash
+echo 'source <(karmadactl completion bash)' >>~/.bashrc
+```
+
+- Add the completion script to the /etc/bash_completion.d directory:
+
+```bash
+karmadactl completion bash >/etc/bash_completion.d/karmadactl
+```
+
+If you have an alias for karmadactl, you can extend shell completion to work with that alias:
+
+```bash
+echo 'alias km=karmadactl' >>~/.bashrc
+echo 'complete -F __start_karmadactl km' >>~/.bashrc
+```
+
+> **Note:** bash-completion sources all completion scripts in /etc/bash_completion.d.
+
+Both approaches are equivalent. After reloading your shell, karmadactl autocompletion should be working.
+
+## Enable kubectl-karmada autocompletion
+Currently, kubectl plugins do not support autocomplete, but it is already planned in [Command line completion for kubectl plugins](https://github.com/kubernetes/kubernetes/issues/74178). 
+
+We will update the documentation as soon as it does.