Adding a new installation method to the README

[lunrenyi]

• Hi, we have implemented a lightweight package manager using shell and awk.
  It helps you download dua release packages from the internet and extract them into a unified directory for management, without requiring root permissions.

• I mean, can the installation method provided by x-cmd be added to the dua README?The installation method for the x command

  x env use dua

Looking forward to your reply :) !