docs(README): add changelog command

Author: Lee-W

docs/README.md

@@ -77,29 +77,34 @@ cz c
 ```bash
 $ cz --help
 usage: cz [-h] [--debug] [-n NAME] [--version]
-        {ls,commit,c,example,info,schema,bump} ...
+          {init,commit,c,ls,example,info,schema,bump,changelog,ch,check,version}
+          ...
 
 Commitizen is a cli tool to generate conventional commits.
 For more information about the topic go to https://conventionalcommits.org/
 
 optional arguments:
--h, --help            show this help message and exit
---debug               use debug mode
--n NAME, --name NAME  use the given commitizen
---version             get the version of the installed commitizen
+  -h, --help            show this help message and exit
+  --debug               use debug mode
+  -n NAME, --name NAME  use the given commitizen (default:
+                        cz_conventional_commits)
+  --version             get the version of the installed commitizen
 
 commands:
-{ls,commit,c,example,info,schema,bump}
-    ls                  show available commitizens
+  {init,commit,c,ls,example,info,schema,bump,changelog,ch,check,version}
+    init                init commitizen configuration
     commit (c)          create new commit
+    ls                  show available commitizens
     example             show commit example
     info                show information about the cz
     schema              show commit schema
     bump                bump semantic version based on the git log
+    changelog (ch)      generate changelog (note that it will overwrite
+                        existing file)
+    check               validates that a commit message matches the commitizen
+                        schema
     version             get the version of the installed commitizen or the
                         current project (default: installed commitizen)
-    check               validates that a commit message matches the commitizen schema
-    init                init commitizen configuration
 ```
 
 ## FAQ