Add new swh-utils image for init-container image

They add some required dependencies to help substituting environment variables, ...

Refs. sysadm-environment#5179

apps/swh-utils/Dockerfile

+FROM debian:bookworm-slim
+
+RUN apt-get -y update && \
+    apt-get -y upgrade && \
+    apt-get install -y gettext-base curl && \
+    apt clean

apps/swh-utils/README.md

+swh-utils
+=========
+
+A docker image with extra deployment (gettext, curl, ...). This will help creating
+init-container which installs configuration files with substituted environment
+variables.