translations: add dockerfile

To avoid transifex versioning problems, use docker to
update translations.

Change-Id: I1de7b7c3ef1feb20935c025e30dad8edf8c62758

docker/Dockerfile_tx

+FROM ubuntu:22.04
+
+USER root
+
+RUN apt-get clean && \
+    apt-get update && \
+    apt-get install -y -o Acquire::Retries=2 \
+    curl \
+    zip
+
+RUN curl -o- https://raw.githubusercontent.com/transifex/cli/master/install.sh | bash
+
+ENV PATH="${HOME}/tx:${PATH}"
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