Stop copying node_modules into frontend image

By not having a .dockerignore file we are including the node_modules
directory in the frontend image, and then installing all the packages a
second time in the build phase when we run npm ci. We now let npm ci do
that work as it's supposed to.

frontend/update-harbor-image.sh

@@ -10,6 +10,12 @@ APP_NAME="greg-frontend"
 CONTAINER="${REPO}/${PROJECT}/${APP_NAME}"
 IMAGE_TAG="${CONTAINER}:${GIT_BRANCH}-${GIT_SHA}"
 
+echo "Generating .dockerignore"
+echo ".*
+*" > .dockerignore
+git ls-tree --name-only HEAD | sed 's/^/!/' >> .dockerignore
+echo "**/node_modules" >> .dockerignore
+
 if command -v podman > /dev/null 2>&1; then
   BUILDER=$(command -v podman)
 else