Add Dockerfile and build script for multi-arch build

Dockerfile

@@ -0,0 +1,35 @@
+FROM alpine:latest
+
+# Install jq, curl and ca-certificates
+RUN apk add --no-cache jq curl ca-certificates bash tar
+
+# Create a directory for speedtest
+WORKDIR /app
+
+# Download the appropriate speedtest binary based on architecture
+ARG TARGETARCH
+# Download the appropriate speedtest binary based on architecture
+RUN set -ex; \
+    if [ "$TARGETARCH" = "amd64" ]; then \
+        ARCH="x86_64"; \
+    elif [ "$TARGETARCH" = "arm64" ]; then \
+        ARCH="aarch64"; \
+    elif [ "$TARGETARCH" = "arm" ]; then \
+        ARCH="armhf"; \
+    else \
+        echo "Unsupported architecture: $TARGETARCH" && exit 1; \
+    fi; \
+    URL="https://install.speedtest.net/app/cli/ookla-speedtest-1.2.0-linux-${ARCH}.tgz"; \
+    echo "Downloading speedtest from: $URL"; \
+    curl -sSLo speedtest.tgz "$URL"; \
+    tar zxvf speedtest.tgz speedtest; \
+    rm speedtest.tgz; \
+    mv speedtest /usr/local/bin/; \
+    chmod +x /usr/local/bin/speedtest
+
+# Copy the script
+COPY send-speedtest.sh /usr/local/bin/send-speedtest.sh
+RUN chmod +x /usr/local/bin/send-speedtest.sh
+
+# Run the script by default
+ENTRYPOINT ["/usr/local/bin/send-speedtest.sh"]