echobot: add echo bot for trying out sending

cmdeploy/src/cmdeploy/__init__.py

@@ -88,10 +88,12 @@ def _install_remote_venv_with_chatmaild(config) -> None:
     for fn in (
         "doveauth",
         "filtermail",
+        "echobot",
     ):
         params = dict(
             execpath=f"{remote_venv_dir}/bin/{fn}",
             config_path=remote_chatmail_inipath,
+            remote_venv_dir=remote_venv_dir,
         )
         source_path = importlib.resources.files("chatmaild").joinpath(f"{fn}.service.f")
         content = source_path.read_text().format(**params).encode()