feat: add github action for docker build on release (#132)

* feat: add github action
Add github action for auto build slim torrverser alpine image with ffmpeg for linux/386,linux/amd64,linux/arm/v6,linux/arm/v7,linux/arm64,linux/ppc64le platforms

* build: move creating dirs and files to entrypoint

* fix: remove linux/386 and linux/ppc64le from docker building

* fix: update readme with docker info

Dockerfile

@@ -0,0 +1,60 @@
+### FRONT BUILD START ###
+FROM --platform=$BUILDPLATFORM node:16-alpine as front
+COPY ./web /app
+WORKDIR /app
+# Build front once upon multiarch build
+RUN yarn install && yarn run build
+### FRONT BUILD END ###
+
+### BUILD TORRSERVER MULTIARCH START ###
+FROM --platform=$BUILDPLATFORM golang:1.17-alpine as builder
+
+COPY . /opt/src
+COPY --from=front /app/build /opt/src/web/build
+
+WORKDIR /opt/src
+
+ARG TARGETARCH
+
+# Step for multiarch build with docker buildx
+ENV GOARCH=$TARGETARCH
+
+# Build torrserver
+RUN apk add --update g++ \
+&& go run gen_web.go \
+&& cd server \
+&& go clean -i -r -cache \
+&& go mod tidy \
+&& go build -ldflags '-w -s' --o "torrserver" ./cmd 
+### BUILD TORRSERVER MULTIARCH END ###
+
+
+### UPX COMPRESSING START ###
+FROM debian:buster-slim as compressed
+
+COPY --from=builder /opt/src/server/torrserver ./torrserver
+
+RUN apt-get update && apt-get install -y upx-ucl && upx --best --lzma ./torrserver
+# Compress torrserver only for amd64 and arm64 no variant platforms
+# ARG TARGETARCH
+# ARG TARGETVARIANT
+# RUN if [ "$TARGETARCH" == 'amd64' ]; then compress=1; elif [ "$TARGETARCH" == 'arm64' ] && [ -z "$TARGETVARIANT"  ]; then compress=1; else compress=0; fi \
+# && if [[ "$compress" -eq 1 ]]; then ./upx --best --lzma ./torrserver; fi
+### UPX COMPRESSING END ###
+
+### BUILD MAIN IMAGE START ###
+FROM alpine
+
+ENV TS_CONF_PATH="/opt/ts/config"
+ENV TS_LOG_PATH="/opt/ts/log"
+ENV TS_TORR_DIR="/opt/ts/torrents"
+ENV TS_PORT=8090
+ENV GODEBUG=madvdontneed=1
+
+COPY --from=compressed ./torrserver /usr/bin/torrserver
+COPY ./docker-entrypoint.sh /docker-entrypoint.sh
+
+RUN apk add --no-cache --update ffmpeg
+
+CMD /docker-entrypoint.sh
+### BUILD MAIN IMAGE end ###