Dynamically load Element Web modules in Docker entrypoint (#29346)

* Dynamically load Element Web modules in Docker entrypoint

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>

* Iterate

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>

* Drop environment for PR runs

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>

* Iterate

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>

---------

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>

Dockerfile

@@ -1,3 +1,5 @@
+# syntax=docker.io/docker/dockerfile:1.7-labs
+
 # Builder
 FROM --platform=$BUILDPLATFORM node:22-bullseye AS builder
 
@@ -8,7 +10,7 @@ ARG JS_SDK_BRANCH="master"
 
 WORKDIR /src
 
-COPY . /src
+COPY --exclude=docker . /src
 RUN /src/scripts/docker-link-repos.sh
 RUN yarn --network-timeout=200000 install
 RUN /src/scripts/docker-package.sh
@@ -19,11 +21,15 @@ RUN cp /src/config.sample.json /src/webapp/config.json
 # App
 FROM nginx:alpine-slim
 
+# Install jq and moreutils for sponge, both used by our entrypoints
+RUN apk add jq moreutils
+
 COPY --from=builder /src/webapp /app
 
 # Override default nginx config. Templates in `/etc/nginx/templates` are passed
 # through `envsubst` by the nginx docker image entry point.
 COPY /docker/nginx-templates/* /etc/nginx/templates/
+COPY /docker/docker-entrypoint.d/* /docker-entrypoint.d/
 
 # Tell nginx to put its pidfile elsewhere, so it can run as non-root
 RUN sed -i -e 's,/var/run/nginx.pid,/tmp/nginx.pid,' /etc/nginx/nginx.conf