Official image - https://hub.docker.com/_/mediawiki
Github source - https://github.com/wikimedia/mediawiki-docker
Installation guide - https://www.mediawiki.org/wiki/Docker/Hub

This image does not provide any additional PHP extensions or other libraries, even if they are required by popular plugins. If you need additional PHP extensions, you'll need to create your own image from this one. Documentation how to install extension

Probably we should create our own Dockerfile using GitHub source examples.
If we use 1.37 version we should add extensions by docker-php-ext-install script like:

docker-php-ext-install -j "$(nproc)" \
       calendar \
       intl \
       mbstring \
       mysqli \
       opcache \
	pluggableAuth \
	openIDConnect \
   ; \
   \

If we use dev version we could add/install it as submodule like:

# Extensions
git submodule update --init --recursive PluggableAuth; \
git submodule update --init --recursive OpenIDConnect; \

Also we should create docker-compose.yml with the right configuration, example in readme file.

The decision was made to:
Get official image
Update it using git submodule with official extensions and custom once.
We will enable extensions in CustomSettings.php which will be automatically included in LocalSettings.php during deploy.
Sensitive data will be passed to LocalSettings.php with env variables.