Add the example for WasmEdge + Kafka / Redpanda + MySQL application to take messages from a queue and save into a database table.

Signed-off-by: Michael Yuan <michael@secondstate.io>

wasmedge-kafka-mysql/etl/Dockerfile

@@ -0,0 +1,26 @@
+FROM --platform=$BUILDPLATFORM rust:1.64 AS buildbase
+RUN <<EOT bash
+    set -ex
+    apt-get update
+    apt-get install -y \
+        git \
+        clang
+    rustup target add wasm32-wasi
+EOT
+# This line installs WasmEdge including the AOT compiler
+RUN curl -sSf https://raw.githubusercontent.com/WasmEdge/WasmEdge/master/utils/install.sh | bash
+
+FROM buildbase AS build
+COPY Cargo.toml .
+COPY src ./src 
+# Build the Wasm binary
+RUN --mount=type=cache,target=/usr/local/cargo/git/db \
+    --mount=type=cache,target=/usr/local/cargo/registry/cache \
+    --mount=type=cache,target=/usr/local/cargo/registry/index \
+    cargo build --target wasm32-wasi --release
+# This line builds the AOT Wasm binary
+RUN /root/.wasmedge/bin/wasmedgec target/wasm32-wasi/release/kafka.wasm kafka.wasm
+
+FROM scratch
+ENTRYPOINT [ "kafka.wasm" ]
+COPY --link --from=build /kafka.wasm /kafka.wasm