Add jq to 3scale toolbox image

3scale toolbox can output JSON content, and having `jq` available makes sense.

A workaround in the meanwhile, can be to build a personalized image using the toolbox image as a base and install jq from there.

To do this create a Dockerfile with the following contents:

FROM registry.redhat.io/3scale-amp2/toolbox-rhel8:3scale2.14
USER root
RUN dnf install -y jq
USER 1001

Build the image with the tag toolbox (the tag is arbitrary):

docker build -t toolbox .

Run the new image using the toolbox tag:

docker run -it toolbox jq --version