adding a click example command.

Example:

can be executed as and just replies 'bar'

```bash
❯ pymcs foo
bar
```

Author: chris-aeviator

src/pymc_server/cli.py

@@ -4,6 +4,6 @@
 def cli():
     pass
 
-    @cli.command()
-    def foo():
-        click.echo('bar')
+@cli.command()
+def foo():
+    click.echo('bar')