Fix voice in container

Dockerfile

@@ -1,6 +1,7 @@
-FROM python:3
+FROM python:3.9.1-alpine
 WORKDIR /usr/src/app
 COPY requirements.txt ./
+RUN apk add ffmpeg musl-dev linux-headers gcc libffi-dev make opus
 RUN pip install --no-cache-dir -r requirements.txt
 COPY . .
 CMD ["bot.py"]