Add untested dockerfile

Dockerfile

@@ -0,0 +1,20 @@
+FROM docker.io/alpine:3.8
+
+ENV UID=1338 \
+    GID=1338
+
+COPY . /opt/maubot
+WORKDIR /opt/maubot
+RUN apk add --no-cache \
+      python3-dev \
+      build-base \
+      py3-aiohttp \
+      py3-sqlalchemy \
+      py3-attrs \
+      ca-certificates \
+      su-exec \
+ && pip3 install -r requirements.txt -r optional-requirements.txt
+
+VOLUME /data
+
+CMD ["/opt/mautrix-telegram/docker-run.sh"]