Add Dockerfile_whatsappmulti for building with WhatsApp Multi-Device support (Whatsmeow) (#1774)

Co-authored-by: Tobias Niepel <tobias.niepel@obi.de>

Dockerfile_whatsappmulti

@@ -0,0 +1,14 @@
+FROM alpine AS builder
+
+COPY . /go/src/matterbridge
+RUN apk --no-cache add go git \
+        && cd /go/src/matterbridge \
+        && CGO_ENABLED=0 go build -tags whatsappmulti -mod vendor -ldflags "-X github.com/42wim/matterbridge/version.GitHash=$(git log --pretty=format:'%h' -n 1)" -o /bin/matterbridge
+
+FROM alpine
+RUN apk --no-cache add ca-certificates mailcap
+COPY --from=builder /bin/matterbridge /bin/matterbridge
+RUN mkdir /etc/matterbridge \
+  && touch /etc/matterbridge/matterbridge.toml \
+  && ln -sf /matterbridge.toml /etc/matterbridge/matterbridge.toml
+ENTRYPOINT ["/bin/matterbridge", "-conf", "/etc/matterbridge/matterbridge.toml"]