docs: add section on how to retrieve user list (#17798)

previews
- [admin/users](https://coder.com/docs/@export-coder-users/admin/users)
-
[reference/cli/users](https://coder.com/docs/@export-coder-users/reference/cli/users)

followup to slack thread:

> Tim
> what's the best way for customers to export a list of Coder users?
>
> @ericpaulsen
> the `/api/v2/users` API route returns all users in the deployment
(along with other information - email, status, username, etc.). from
<https://coder.com/docs/reference/api/users#get-users>


- adds an easy-to-find section to the admin/users doc
- updates the cli commands with short descriptions

---------

Co-authored-by: EdwardAngert <17991901+EdwardAngert@users.noreply.github.com>
Co-authored-by: M Atif Ali <atif@coder.com>

cli/usercreate.go

@@ -28,7 +28,8 @@ func (r *RootCmd) userCreate() *serpent.Command {
 	)
 	client := new(codersdk.Client)
 	cmd := &serpent.Command{
-		Use: "create",
+		Use:   "create",
+		Short: "Create a new user.",
 		Middleware: serpent.Chain(
 			serpent.RequireNArgs(0),
 			r.InitClient(client),