Update nixpacks.toml

nixpacks.toml

@@ -2,6 +2,6 @@ providers = ['python']
 
 [phases.setup]
 nixPkgs = ['python310']
-cmds = ['apt-get update','apt-get install -y --no-install-recommends ffmpeg espeak']
+cmds = ['apt-get update','apt-get install -y --no-install-recommends ffmpeg espeak','python -m venv /opt/venv && . /opt/venv/bin/activate && pip install -r requirements-optional.txt']
 [start]
 cmd = "python ./app.py"