docs(appium): add CLI intro doc
MODIFY
packages/appium/docs/en/cli/index.md
packages/appium/docs/en/cli/index.md
title: CLI Intro
---
-TODO
+When you install Appium globally from NPM, an `appium` "binary" is placed in your global
+`node_modules` folder. If your `PATH` is set up to look for programs in that folder, then you will
+be able to run `appium` from the command line of your terminal. The `appium` program has two main
+subcommands, each of which has its own set of documentation:
+
+1. The [Server](./args.md) subcommand starts an Appium server listening for new session requests,
+ and takes a variety of parameters related to the operation of the server and also those consumed
+ by active drivers or plugins.
+2. The [Extension](./extensions) subcommands assist in managing Appium drivers and plugins.

docs(appium): add CLI intro doc