add dockerfile

Dockerfile

+FROM --platform=$BUILDPLATFORM public.ecr.aws/docker/library/alpine:3.21.0 AS ca-certs
+FROM --platform=$BUILDPLATFORM tonistiigi/xx:1.6.1 AS xx
+FROM --platform=$BUILDPLATFORM public.ecr.aws/docker/library/golang:1.23.3 AS build
+ARG TARGETPLATFORM
+COPY --from=xx / /
+WORKDIR /app
+COPY go.mod go.sum ./
+RUN go mod download
+COPY ./ ./
+RUN CGO_ENABLED=0 GOOS=linux xx-go build -ldflags "-w -s" -o /imgshare
+
+FROM scratch
+ENV GIN_MODE=release
+COPY --from=ca-certs /etc/ssl /etc/ssl
+COPY --from=build /imgshare /imgshare
+ENTRYPOINT ["/imgshare"]
+