docker: fix deps

Dockerfile

@@ -3,11 +3,11 @@ FROM python:3.7-alpine
 COPY requirements.txt /
 
 RUN apk add --update --no-cache --virtual .tmp-build-deps \
-    make libffi-dev musl-dev gcc \
-    && apk add ffmpeg \
+    make gcc \
+    && apk add ffmpeg musl-dev libffi-dev libsodium-dev opus-dev \
     && pip3 install -r /requirements.txt
 
-COPY audio /moai
+ADD audio /moai/audio
 COPY settings.json /moai
 COPY moai.py /moai