Update Dockerfile

Dockerfile

 FROM alpine:latest
 
 RUN set -ex \
+    && pkg add --virtual .build-deps build-base \
     && apk add --no-cache git python3 \
     && python3 -m ensurepip \
-    && pip3 install -r requirements.txt
+    && pip3 install -r requirements.txt \
+    && apk del .build-deps
 
 WORKDIR /docs
 VOLUME /docs