Add docker bake environment

with support for building an Element Web docker image with build & runtime module loader
with support for building docker images with a module pre-baked in

packages/element-web-module-api/Dockerfile

@@ -0,0 +1,19 @@
+ARG ELEMENT_VERSION=latest
+FROM vectorim/element-web:${ELEMENT_VERSION}
+ARG ELEMENT_WEB_MODULES=""
+
+# Override default nginx config. Templates in `/etc/nginx/templates` are passed
+# through `envsubst` by the nginx docker image entry point.
+COPY /docker/nginx-templates/* /etc/nginx/templates/
+COPY /docker/docker-entrypoint.d/* /docker-entrypoint.d/
+
+# Create directories before we gain privileges
+RUN mkdir -p /tmp/element-web-config /tmp/element-web-modules
+
+# Escalate privileges to install jq and moreutils and run the fetch modules script
+USER root
+RUN apk add jq moreutils
+RUN ELEMENT_WEB_MODULES=${ELEMENT_WEB_MODULES} /docker-entrypoint.d/17-fetch-element-modules.sh
+
+# Drop privileges back to nginx
+USER nginx