docs: update usage info in CLI README (#1305)

### Summary of Changes

Update the usage information in the CLI README to include all current
commands.

packages/safe-ds-cli/README.md

@@ -1,5 +1,7 @@
 # Safe-DS CLI
 
+Command-line tooling for the [Safe-DS](https://github.com/Safe-DS/DSL) programming language for safe data science.
+
 ```txt
 Usage: cli [options] [command]
 
@@ -9,6 +11,8 @@ Options:
 
 Commands:
   check [options] <paths...>     check Safe-DS code
+  document [options] <paths...>  generate Markdown documentation
+  format <paths...>              format Safe-DS code
   generate [options] <paths...>  generate Python code
   help [command]                 display help for command
 ```