Fix Docker build for develop and publish a /version file

Fixes https://github.com/vector-im/riot-web/issues/10426

Dockerfile

@@ -21,6 +21,9 @@ RUN yarn build
 # Copy the config now so that we don't create another layer in the app image
 RUN cp /src/config.sample.json /src/webapp/config.json
 
+# Ensure we populate the version file
+RUN dos2unix /src/scripts/docker-write-version.sh && sh /src/scripts/docker-write-version.sh
+
 
 # App
 FROM nginx:alpine