added dyndns Docker image

dyndns/Dockerfile

@@ -0,0 +1,12 @@
+FROM alpine:3.22
+
+RUN --mount=type=cache,target=/var/cache/apk apk add python3 pipx
+RUN addgroup -S dyndns
+RUN adduser -D -S -h /var/lib/dyndns -G dyndns dyndns
+
+ADD --chown=dyndns:dyndns pip.conf /var/lib/dyndns/.pip/pip.conf
+
+USER dyndns
+WORKDIR /var/lib/dyndns
+RUN pipx install wdyndns
+ENV PATH="/var/lib/dyndns/.local/bin:$PATH"