feat(docker): include essentia extractor binary in container image (#162)

* Include essentia extractor binary in container image

Essentia provides binaries for x86_64 Linux and i686.
The 32 bit binaries are not included as it is unlikely that they will be used.
The `essentia-extractors` stage will only execute for 64 bit image builds.

* fixup! correction

Co-authored-by: Senan Kelly <senan@senan.xyz>

* fixup! mistake

* pin version; copy with * to work on other platforms; extract only the binary to /tmp

closes #161

---------

Co-authored-by: Senan Kelly <senan@senan.xyz>

Author: tandy-1000

Dockerfile

@@ -12,12 +12,23 @@ RUN  \
     --mount=type=cache,target=/root/.cache/go-build \
     CGO_ENABLED=0 GOOS=$TARGETOS GOARCH=$TARGETARCH go build -o /out/ ./cmd/...
 
+FROM alpine:3.22 AS essentia-extractors
+ARG VERSION="v2.1_beta2"
+ARG TARGETARCH
+WORKDIR /tmp
+RUN if [ "$TARGETARCH" = "amd64" ]; then \
+    apk add --no-cache curl tar; \
+    curl -fL -o essentia-extractors.tar.gz https://essentia.upf.edu/extractors/essentia-extractors-${VERSION}-linux-x86_64.tar.gz; \
+    tar -xzf essentia-extractors.tar.gz --strip-components=1 -- essentia-extractors-${VERSION}/streaming_extractor_music; \
+    fi
+
 FROM alpine:3.22
 LABEL org.opencontainers.image.source=https://github.com/sentriz/wrtag
 RUN apk add -U --no-cache \
     su-exec \
     rsgain
 COPY --from=builder /out/* /usr/local/bin/
+COPY --from=essentia-extractors /tmp/streaming_extractor_music* /usr/local/bin/
 COPY docker-entry /
 ENTRYPOINT ["/docker-entry"]
 CMD ["wrtagweb"]