Dockerfile: Move to smaller alpine base image

Signed-off-by: lzzy12 <jhashivam2020@gmail.com>

Dockerfile

@@ -1,16 +1,27 @@
-FROM ubuntu:18.04
+FROM python:3-alpine
+
+WORKDIR /bot
+RUN chmod 777 /bot
+
+# install ca-certificates so that HTTPS works consistently
+RUN apk add --no-cache --update \
+      ca-certificates \
+      aria2 \
+      libmagic \
+      python3-lxml \
+      curl \
+      pv \
+      jq
+
+RUN apk add --no-cache --update --virtual .build-deps \
+      build-base \
+      libffi-dev \
+      openssl-dev
 
-WORKDIR /usr/src/app
-RUN chmod 777 /usr/src/app
-RUN apt -qq update
-RUN apt -qq install -y aria2 python3 python3-pip locales python3-lxml curl pv jq
 COPY requirements.txt .
 RUN pip3 install --no-cache-dir -r requirements.txt
+RUN apk del .build-deps
 COPY . .
-RUN chmod +x aria.sh
-RUN locale-gen en_US.UTF-8
-ENV LANG en_US.UTF-8
-ENV LANGUAGE en_US:en
-ENV LC_ALL en_US.UTF-8
+RUN chmod +x *.sh
 
-CMD ["bash","start.sh"]
+CMD ["sh", "./start.sh"]