Fix Docker cointainer build

libyaml-dev got removed in the base image in
docker-library/ruby@7f078b1.

While this change did get reverted in
docker-library/ruby@6f84caa
it will be removed in the next Ruby version, so we as well fix it now.

Dockerfile

@@ -18,7 +18,7 @@ FROM base AS build
 
 # Install packages needed to build gems
 RUN apt-get update -qq && \
-    apt-get install --no-install-recommends -y build-essential git libvips pkg-config libpq-dev nodejs npm yarn
+    apt-get install --no-install-recommends -y build-essential git libvips pkg-config libpq-dev libyaml-dev nodejs npm yarn
 
 # Install application gems
 COPY Gemfile Gemfile.lock ./