Updated adminer dark theme support

[M46N3]

Added a new environment variable to support new dark mode functionality.

Fixes #198
Fixes #218

Updated docs PR docker-library/docs#2577

[M46N3]

Any chance this can be merged soon? Maybe together with upgrade to 5.4.0 #221?

[TimWolla]

Hi! Thank you for the PR. Unfortunately I've not yet had the time to investigate this and I don't want to commit to a particular “easy” solution that might not be the best solution within the context of this Docker image.

[stasadev]

Wouldn't it be simpler to handle it like this?

if [ -n "$ADMINER_DESIGN" ]; then
	# Only create link on initial start, to ensure that explicit changes to
	# adminer.css after the container was started once are preserved.
	if [ ! -e .adminer-init ]; then
-		ln -sf "designs/$ADMINER_DESIGN/adminer.css" .
+		for css_file in adminer.css adminer-dark.css; do
+			if [ -f "designs/$ADMINER_DESIGN/$css_file" ]; then
+				ln -sf "designs/$ADMINER_DESIGN/$css_file" adminer.css
+				break
+			fi
+		done
	fi
fi

This avoids introducing an extra variable.

[M46N3]

I am not sure persisting changes to a theme is desired as a default? If personal changes are needed it could maybe be solved with mounting your own css?

The extra variable is required to give the user a choice between light and dark mode.