add x-cmd to shells list

[curry798]

Hi. Thank you for this collection of useful terminal programs! I want to add x-cmd to the list. I have searched the PRs of this repo and believe that this is not a duplicate.

x-cmd is a toolset implemented using posix shell and awk. It is very small in size and offers many interesting features.

Tools Provided by x-cmd:

• Wrappers for Common Commands (e.g., cd, ip, ps, tar, apt, brew): These wrapped commands are more intelligent and easier to use compared to the native commands.
• Lightweight Package Management Tool: We have implemented a lightweight package management tool using shell and awk. Through it, you can quickly obtain most common software tools, such as jq, 7za, bat, nvim, python, node, go, etc.
• CLI for Useful Websites (e.g., github.com, cht.sh): We have wrapped their APIs using shell and awk for daily use and to obtain corresponding services in scripts.
• AI Tools: We provide CLIs for ChatGPT, Gemini, Jina.ai, etc., and have wrapped corresponding shortcut commands for different application scenarios, such as @gemini for chatting with Gemini AI and @zh for using AI to translate specified content or command results.