Add docker image

Dockerfile

@@ -0,0 +1,23 @@
+FROM golang:1.19-alpine AS builder
+LABEL maintainer="nekohasekai <contact-git@sekai.icu>"
+COPY . /go/src/github.com/sagernet/sing-box
+WORKDIR /go/src/github.com/sagernet/sing-box
+ARG GOPROXY=""
+ENV GOPROXY ${GOPROXY}
+ENV CGO_ENABLED=0
+RUN set -ex \
+    && apk add git build-base \
+    && export COMMIT=$(git rev-parse HEAD) \
+    && go build -v -trimpath -tags 'with_quic,with_wireguard,with_clash_api' \
+        -o /go/bin/sing-box \
+        -ldflags "-X github.com/sagernet/sing-box/constant.Commit=${COMMIT} -w -s -buildid=" \
+        ./cmd/sing-box
+FROM alpine AS dist
+LABEL maintainer="nekohasekai <contact-git@sekai.icu>"
+RUN [ ! -e /etc/nsswitch.conf ] && echo 'hosts: files dns' > /etc/nsswitch.conf
+RUN set -ex \
+    && apk upgrade \
+    && apk add bash tzdata ca-certificates \
+    && rm -rf /var/cache/apk/*
+COPY --from=builder /go/bin/sing-box /usr/local/bin/sing-box
+ENTRYPOINT ["sing-box"]